Electrical Headache! please help.. 96 cav

Since this past fall i've been trying to get my sisters cavalier fixed. It started with a no spark condition. So i replaced the ckp, coils, and the ICM, to no avail, then finally one day i had the brilliant idea of checking the PCM. Long story short, it came out in 2 pieces and was more corroded then you can imagine! Along with that, the plugs were also very corroded. So i spliced in 3 'new' junkyard PCM plugs, along with a pcm. Finally the car starts, but only for 2 seconds before passlock shuts her down. I tried the 10 minute re-learn procedure, and also had the pcm reflashed, but its not recognizing the re flash! Anti-theft still shuts the car down. I'm at a loss now. If anybody can give me some suggestions/help, i would really appreciate it. Should i be testing for continuity/resistance in some wires between the ignition switch/ICM/PCM related to the passlock??

by the way its the base model, with the 2.2. I believe that was the only motor produced in 96, and all cavaliers had the same ecu for that year as well. Any ideas guys! I'm trying to fix her and have hit a roadblock, not sure where to look now.

Does the vehicle have a Mass Air Flow sensor ?

I had a vehicle that acted like it was the security system shutting it down, turned out to be the MAF.

Just a thought.

no that is not the problem, it is involved in some wiring with the ecu and passlock system but i dont know how to diagnose it, hopefully somebody here will chime in!

any help from you electrical gurus?

Usually with a passlock problem you have to either replace or bypass the lock cylinder. I reccomend bypassing it simply because of cost, of course you won't have any anti-theft system any more. To bypass it, simply cut the signal and ground wires from the BCM and solder a resistor inline on the BCM side of the wires. There is a range of resistors that will work, if the resistance of your lock cylinder is high, replace it with a low resistor. If it's low, replace with high and replace middle with either end. I have a table of the recognizable resistor values at work, which I will post if I can remember to :) The reason you should change the resistance as much as possible is that it won't relearn if the value is really close to what's in there now.

Thanks tons for the help, i may have to just do that then. I feel like i would have to keep fishing alot to find the current problem. but before i bypass, i'll see if i can do a few more tests. By the way, i'm embarrassed to say, but i'm not familiar with the 'bcm', only the pcm, and the icm. I thought the icm and pcm were the only 2 systems in line with the passlock system. Just to confirm also, are the wires you're talking about, 3 wires that come right up to the ignition assembly?

Hey ,finally the weather is warm enought to try and work on a few of these wires. If anybody could give me a bit more advice with the bypass procedure that would be great. I think i understand how to do it, but any extra clear advice would be appreciated! I'm confused as to where to place the leads to measure resistance, ie ignition side of the cut yellow wire or dash side, along with the ground wire. Also, how am i supposed to measure resistance accurately when i can only actually start the car for about 1 - 2 seconds at most?! I was led to believe that the car needs to be running before the resistance measurements will be what i'm looking for. Thanks for the help!

With your electrical problems you need a good wiring diagram.
http://www.alldata.com/ Sells a years subscription for around $29.95.
Your getting some good advise but I've found to many poor wiring splices to be confident this isn't your problem. You need to unplug the connections which were spliced. Use an ohm meter and ohm each wire. If you don't have a good set of crimping pliers or didn't solder them this is very important.

I infact have just done this, and the splicing seems to be doing a solid job, everything is 'ohming out', and all compenents receiving the correct signal from what i can tell. I would like to try this bypass, but am still unclear as to what to do. I'm still not quite sure which wire to cut, there is a ribbon of wires on top of the column that are surely smaller than 20GA that i thought were the passlock wires, and then another article said it was a 20GA yellow wire not in ribbon with other wires, on the underside of the tumbler. So i'm getting confused to say the least, a quick overview might help.

I got your e-mail. In the future, please do not e-mail anyone for help. I'm pretty sure that's in the "User Guidelines", if not, it should be. When I have free time, I'm more than happy to help. When I have free time, I'm usually here. Not a huge deal to me, but it went straight to the "deleted" folder.

There are 3 wires that come out of the lock cylinder. Red, Black, and yellow ( I think, it can vary from model to model, and honestly I don't think I've seen this problem on a Cavalier, so it's possible that the wire colors are different from the W and N bodies that I've done so many of). I usually cut the wires as close to the BCM as I can get, but you'll need a wiring diagram to identify which connector/terminal it is. There's nothing wrong with doing it at the lock cylinder, but I like to eliminate a fault in the wire as the problem. All you do is cut the yellow and black wires and solder the resistor between them. What I like do is cut 2x 3" sections of wire and solder them to the resistor on my workbench because it's so much easier there. Solder the wires on so the open ends are facing the same direction, then put two layers of heat shrink tubing over the resistor leads, that makes it stiffer, so the leads on the resistor won't break. Also, use 1/8 watt resistors (the blue ones), the little brown ones aren't rated high enough for this.
-----------------\
------/\/\/-------| <-- solder the wires on like this


Then, if it's very difficult to solder it in the vehicle, I'll just crimp two heatshrink butt-connectors to the short wires and only crimp the resistor in. I like to solder everything when possible, but depending on the space you have, you may be unable to.

Go to http://www.bulldogsecurity.com/ Search vehicle wiring diagrams.
You should find information you need.
You can google passlock 1 or 2 for information. Normally this shuts power to the injectors. Some shuts down the fuel pump.
If you search the forum their is information.

PASSLOCK REPROGRAMMING AUTO LEARN

IMPORTANT: Due to component variability, the vehicle theft deterrent (VTD) system must have the learn procedure performed regardless, if the vehicle starts on the first ignition cycle after a VTD repair.

You must perform a theft relearn procedure if any of the following components have been replaced:

* Passlock Sensor
* Instrument Panel Cluster (IPC)
* Powertrain control module (PCM) The above modules, with the exception for the Passlock Sensor must also be programmed with each module's own vehicle configuration.

AUTO LEARN
Time required, approximately 10 minutes:

1. Insure that the battery is fully charged.
2. Use the scan tool in order to clear the DTCs.
3. Turn the ignition switch from the OFF position to the CRANK position attempting to start the vehicle. The vehicle will start and then stall.
4. Leave the ignition switch in the ON position while observing the security indicator.
5. When the security indicator turns off, which can take up to 10 minutes, turn the ignition switch off. Wait 10 seconds.
6. The BCM and the PCM will learn the new code on the next start attempt.

PASSLOCK REPROGRAMMING AUTO LEARN

IMPORTANT: Due to component variability, the vehicle theft deterrent (VTD) system must have the learn procedure performed regardless, if the vehicle starts on the first ignition cycle after a VTD repair.

You must perform a theft relearn procedure if any of the following components have been replaced:

* Passlock Sensor
* Instrument Panel Cluster (IPC)
* Powertrain control module (PCM) The above modules, with the exception for the Passlock Sensor must also be programmed with each module's own vehicle configuration.

AUTO LEARN
Time required, approximately 10 minutes:

1. Insure that the battery is fully charged.
2. Use the scan tool in order to clear the DTCs.
3. Turn the ignition switch from the OFF position to the CRANK position attempting to start the vehicle. The vehicle will start and then stall.
4. Leave the ignition switch in the ON position while observing the security indicator.
5. When the security indicator turns off, which can take up to 10 minutes, turn the ignition switch off. Wait 10 seconds.
6. The BCM and the PCM will learn the new code on the next start attempt.

I think this is the solution to your problem. I think when you switched the PCMs the relearn and/or reflash wasn't done properly.

Thanks for the help guys, ill get back to you within a week or so.. As for the reprogramming, it was tried numerous times, using the original eprom chip, and another eprom chip, with a snap-on scan tool, i really feel that the likelyhood of that being done wrong is low. But dont quote me:P.

Thanks for the help guys, ill get back to you within a week or so.. As for the reprogramming, it was tried numerous times, using the original eprom chip, and another eprom chip, with a snap-on scan tool, i really feel that the likelyhood of that being done wrong is low. But dont quote me:P.

This doesn't make much sense to me. A '96 is obd2 and doesn't have a prom chip just a programable prom. Also I don't think a snap-on scanner can program the PCM only a GM Tech2 scanner tool can. That's my understanding of it. It doesn't sound like the PCM got reflashed properly.

This doesn't make much sense to me. A '96 is obd2 and doesn't have a prom chip just a programable prom. Also I don't think a snap-on scanner can program the PCM only a GM Tech2 scanner tool can. That's my understanding of it. It doesn't sound like the PCM got reflashed properly.

Not sure about the chip in 96... but yes, only the Tech2 can program GM cars.

What exactly did you do with the Snap-on scan tool and which model is it?

Not sure about the chip in 96... but yes, only the Tech2 can program GM cars.

Pretty much all '95 GM that I've seen at least are flashed programmed and all '96 up are obd2 and definitely flash programmed. Well you just verified that only a tech2 can program the PCM, so it looks like the original poster never got his PCM programmed.

The problem here may be that i am not giving perfectly accurate information. For one, i simply thought the removable chip was called a prom chip, or eprom chip, and either way i tried reflashing with 2 chips. Second, i thought it was a snap-on scan tool, with a gm program on it. It is not mine, but a fellow that often works on cavaliers and has had to flash them many times.. (according to him). It was a large red handheld scan tool, and he had to input the vin, along with a few other things, and had to let it sit for 5 or 10 minutes while waiting for it to flash. Either this was the gm tool and reflashing doesnt cut it, or he used the wrong tool, and took my money. Sorry for the confusion folks.

Try using contact cleaner and installing the original e prom chip. You can have a bad switch but a resister will take care of this problem.
http://www.ntxtools.com/ Search 3606 This is a picture of a tool but is more than you may want to pay.

The problem here may be that i am not giving perfectly accurate information. For one, i simply thought the removable chip was called a prom chip, or eprom chip, and either way i tried reflashing with 2 chips. Second, i thought it was a snap-on scan tool, with a gm program on it. It is not mine, but a fellow that often works on cavaliers and has had to flash them many times.. (according to him). It was a large red handheld scan tool, and he had to input the vin, along with a few other things, and had to let it sit for 5 or 10 minutes while waiting for it to flash. Either this was the gm tool and reflashing doesnt cut it, or he used the wrong tool, and took my money. Sorry for the confusion folks.

I can't say I've ever heard of GM software for a snap-on scan tool, but if he's done it before, I sure won't argue with that without any experience there myself. We have a Snap-on and a Tech-2, and if the Snap-on was capable of what the Tech-2 is, I don't think the owner of the shop would have spent $7,000 on the Tech-2. The Tech-2, the GM factory tool is dark grey and about half the size of the snap-on scan tools, so it was not the GM tool he used. In the "MODIS", the most popular snap-on scan tool, you have to enter part of the VIN to identify the vehicle, but can't actually do anything for programming. As far as I know, the "Big 3" allow only their scan tool to do programming.

I can't say I've ever heard of GM software for a snap-on scan tool, but if he's done it before, I sure won't argue with that without any experience there myself. We have a Snap-on and a Tech-2, and if the Snap-on was capable of what the Tech-2 is, I don't think the owner of the shop would have spent $7,000 on the Tech-2. The Tech-2, the GM factory tool is dark grey and about half the size of the snap-on scan tools, so it was not the GM tool he used. In the "MODIS", the most popular snap-on scan tool, you have to enter part of the VIN to identify the vehicle, but can't actually do anything for programming. As far as I know, the "Big 3" allow only their scan tool to do programming.

That's my understanding as well that a Snap-on scanner can't programming a GM PCM and neither can any other scanner besides the Vetronix Tech-2 and the Vetronix Mastertech (similar to a Tech 2). I have heard that there's was a standard after '04 that an aftermarket "Passthru" device will allow you to connect a laptop and with a subscription to the GM calibration software you can then program the PCM. But an aftermarket scan tool wouldn't be in the picture anyway. Now, I don't know if this works on pre-'04 but I think so.

I'm still confused about the poster mentioning "chips". If he's talking about the EEPROM I didn't know that was replaceable separately. Maybe he means PCMs, but I'm not sure where he got the 2 different PCMs. OP, why can't you clean up the terminals and put the old PCM back in?

I pulled the original pcm out of the vehicle in 2 pieces it was so corroded, completely unusable. Even the plugs were severely corroded, and i had to splice new plugs in. On the 96 cavaliers i know that they all used the same pcm no matter what options the vehicle had, this pcm has a removable plate, and below that plate is a prom chip that can be easily removed. I got the second pcm out of another cavalier in perfect shape, and so i have 2 prom chips now, one from the original, and one from the 'new' pcm. As for the scan tool, i cant continue to comment, it would just be speculation.

On the 96 cavaliers i know that they all used the same pcm no matter what options the vehicle had

I don't think that's true. I'm 99% sure the 2.2 and 2.4 engines have different PCMs.

Yes, as long as its the 2.2, the pcm will be the same. Ie, even if you pull it from one with an auto tranny, and other options that your car doesnt have, the pcm will still be ok to use.

Yes, as long as its the 2.2, the pcm will be the same. Ie, even if you pull it from one with an auto tranny, and other options that your car doesnt have, the pcm will still be ok to use.

Well a PCM another 96 2.2 from AT car won't work right on a manual car and vice versa. You realize that the PCM has the VIN number of each specific car? I think the replacement PCM is going to need be reflashed. You say you think the vehicle theft system is activating. When you turn the key to ON does the Theft light come and then go off while cranking?

They are completely interchangeable, you just need to have them flashed. You have to understand that the piece of the pcm that stores memory(ie vin), is the eprom chip that i've talked about so many times. When you put in a new one, it requires reflashing, which as i said has been done unsuccessfully. This is specific to 1996 however. It is a solid light prior to crank, and flashes 2 seconds after start which inturn shuts the fuel off, then it goes back to solid.

They are completely interchangeable, you just need to have them flashed. You have to understand that the piece of the pcm that stores memory(ie vin), is the eprom chip that i've talked about so many times. When you put in a new one, it requires reflashing, which as i said has been done unsuccessfully. This is specific to 1996 however. It is a solid light prior to crank, and flashes 2 seconds after start which inturn shuts the fuel off, then it goes back to solid.

Right, it's not going to work until it's reprogrammed. What I was saying is if you put aside the VIN compatibility it could theoretically run fine without reprogramming if the replacement 96 PCM came out of the same engine and transmission, but it's a mute point since it has to be reprogrammed regardless.

Well it sounds like your theft deterrent is shutting the engine down. It's probably not a problem in the theft system its self, it's probably because the PCM has to be reprogrammed to the calibration with that car's VIN to pass theft deterrent.

This company sells rebuilt and also reflashes computers.
http://www.autocomputerexchange.com/Repairs
Call for a price on a reflash.

I just had a look at it today finally, and found that there is a ribbon of 3 wires, going directly into the tumbler, and must be in the 20 ga range they are so small. If a picture would help let me know. My problem is that they are all black. One side of the ribbon has a white stripe down it however. Is this the group of 3 wires i should be concerned with?.. I cant find anything else closer to what has been discribed. There are no 'yellow', and 'white' wires as i was instructed about, but perhaps they weren't always that colour depending on time or location of manufacture?

Those are probably the ones... follow them to where it connects to the main harness under the dash and see if the wire colors match. The wires you're seeing are the "pigtail", they're actually part of the lock cylinder. No original wiring harness will be all one color, so follow them to where you see color. If I remember, I'll take a look at work tomorrow and see if the wiring diagram shows anything. No promises there tho, my short term memory is... uh... what was I saying? ;)

I checked and it says this is a passlock 1 so I would try another key. If this doesn't work use a can of contact cleaner clean the key and use a Q-tip and clean the key lock. If this works you can get the ohm reading and buy a proper resister so when its installed it will work.

The 3 wire connector is the passlock, the wires are probably wrapped in black tape. I don't think the ignition cylinder or the code it's sending to the BCM is the problem. I think the problem is the used PCM doesn't recognize the password from the BCM. And until the PCM is reprogrammed it's not going to relearn the password.

I checked and it says this is a passlock 1 so I would try another key. If this doesn't work use a can of contact cleaner clean the key and use a Q-tip and clean the key lock. If this works you can get the ohm reading and buy a proper resister so when its installed it will work.

Passkey=resistor in key
Passlock=resistor in lock cylinder

Passlock 1 will still have it in the cylinder

Boomer, this is your lucky day, my first vehicle this morning was a '97 cavalier with a passlock problem (but I still forgot to get you that diagram), so assuming 96 and 97 are the same: The 3 black wires come out of the lock cylinder and run under the lock cylinder about 3" and end in a connector where the wire colors change to wht (+), blk (-), and yel (signal). If yours if different and really does only have black wires, the short pigtail on this one had the white stripe on the wire that becomes white after the connector. Looking at the 3 wires with the white stripe on the left, they are white, black, yellow. To be sure, check with a voltmeter. After you rig up the resistor and wires as I described in a previous post, cut the black and yellow wires only. Do not cut the white wire, it is 5v from the Instrument Panel Cluster, and you don't want it shorting to ground anywhere, just leave it plugged in to the lock cylinder when you're done. Also, the passlock system does not go through the BCM as I previously said. The lock cylinder goes to the IPC which goes to the PCM. I forget the range of resistors you can use. Too high or too low doesn't work, the IPC sees the resistance value in "counts" (which I assume end at 255 like all other counts on GM vehicles), not ohms. I used a 3k ohm resistor which read about 130 counts, so 3-5k ohms should be fine.

The resistors for Passlock are in the ignition cylinder. I guess Passlock might not run through the BCM, but Passlock 2 does. As I understand it, to bypass the lock cylinder resistor you can measure the resistance between the yellow wire to the lock cylinder and the black wire and select the same resistance value. Or I guess as J-ri is explaining just pick a fixed resistance value instead.

I don't really see the point in doing this because the PCM will relearn the ignition cylinders code anyway if you follow the password relearn procedure. 1. Turn key to Start and leave key at RUN for 10 mins, then turn key OFF. 2. Turn key to RUN but not START for 10 mins, then turn key to OFF. 3. Repeat step 2 two more times for a total of 3 times. 4. Turn key to START and password is relearned.

If that doesn't reset the theft password and start the car then you have something else wrong with the theft system besides the password/ignition cylinder. Like maybe the used PCM needs to be programmed for this car. Or maybe the problem isn't in the theft system to begin with.

http://members.tripod.com/~autosecurity/PASS1.html (http://members.tripod.com/%7Eautosecurity/PASS1.html)
http://www.car-forums.com/s10/t19652.html
http://www.cardone.com/English/Club/Products/Electronics/Protech/Tech_Bulletins/PT%2070-77-0001.pdf

Lucky day is right.
First off, thanks guys for all the great info, i really appreciate it. It is plenty to go with! I'm lucky to have a few good minds helping me.
In response to Manic.. The problem is that after completely reprogramming and reflashing, my pcm doesnt respond, and when trying the simpler relearn procedures you speak of, it doesnt work either. The theft light simply flashes after the engine is shut down, and then stays solid indefinately! The light does not go out after a period of time.
I will try the resistor bypass method ASAP. If this doesn't work then i will begin to try some other suggestions mentioned here. For now the resistor bypass is the best option for sure.

The resistors for Passlock are in the ignition cylinder. I guess Passlock might not run through the BCM, but Passlock 2 does. As I understand it, to bypass the lock cylinder resistor you can measure the resistance between the yellow wire to the lock cylinder and the black wire and select the same resistance value. Or I guess as J-ri is explaining just pick a fixed resistance value instead.

I don't really see the point in doing this because the PCM will relearn the ignition cylinders code anyway if you follow the password relearn procedure. 1. Turn key to Start and leave key at RUN for 10 mins, then turn key OFF. 2. Turn key to RUN but not START for 10 mins, then turn key to OFF. 3. Repeat step 2 two more times for a total of 3 times. 4. Turn key to START and password is relearned.

If that doesn't reset the theft password and start the car then you have something else wrong with the theft system besides the password/ignition cylinder. Like maybe the used PCM needs to be programmed for this car. Or maybe the problem isn't in the theft system to begin with.

I can't tell you if PL1 doesn't and PL2 does go through the BCM (although while reading up on a supercharger I just bought, I found an article that suggests cavaliers don't have a BCM until '00 model year. I couldn't tell ya, I need to look the info upas I need it) All I know right now is that the '97 does not have a BCM shown in the "theft deterrent" wiring diagram.

The reason I pick a fixed value is that sometimes the resistance isn't re-learned if it's very close to the original, which can cause a problem down the road. We work with a guy that does mostly extreemly complicated, "how is that possible" electrical stuff, and he saw that once so now I always pick a "fixed" value. We recently moved to a larger building, but before we lost it in the move, we had a table of all the valid resistances taped to the wall. What you're supposed to do is look at the PL voltage while cranking and then look to see what resistance it has to be (GM only used like 9 different resistances), then pick the new resistor as far away from the current value as possible. It's one of those things that there's almost no chance I'll ever see it in my lifetime, but if i can avoid a comeback, I'll do it. Also, if the lock cylinder failed, we really don't know how far out it is, maybe it's above or below the min/max ohms.

In response to Manic.. The problem is that after completely reprogramming and reflashing, my pcm doesnt respond, and when trying the simpler relearn procedures you speak of, it doesnt work either.
I thought we already agreed that your replacement PCM never got reprogrammed because the proper passthru or scanner wasn't used?



The theft light simply flashes after the engine is shut down, and then stays solid indefinately! The light does not go out after a period of time.
I will try the resistor bypass method ASAP. If this doesn't work then i will begin to try some other suggestions mentioned here. For now the resistor bypass is the best option for sure.

Well if your light is on indefinitely then there's a problem somewhere that won't allow the PCM to relearn the ignition cylinder password. But again, this is probably because the PCM hasn't been reprogrammed. What I'm saying is bypassing the ignition cylinder is really just bypassing the ignition cylinder resistor code with a new resistor and replacing the passlock code with a new code for the PCM to learn. So unless your problem is just the ignition cylinder, then you're just going to be back to square one with the PCM trying to relearn the password which you said it won't do anyway. Maybe the problem is just the ign cylinder, but I doubt it.

But do you get what I'm saying? All you'll be doing is bypassing the ignition cylinder and directing the PCM to relearn the new resistor value. Which you said it won't go into password relearn, so if the ignition cylinder isn't the problem then it doesn't fix anything.

I think the fix is to reprogram the PCM which it needs anyway, and it will reprogram with the right equipment, or get one that's been reprogrammed for your VIN. That should solve the passlock problem. Also have you checked all the fuses especially ign? It's possible you might have an open or short in the passlock wiring. You would need a voltmeter, maybe a test light and a diagnostic chart to find that though.

Well if your light is on indefinitely then there's a problem somewhere that won't allow the PCM to relearn the ignition cylinder password. But again, this is probably because the PCM hasn't been reprogrammed.

I kindda explained that in the post above (3 minutes before yours) :)

If the cylinder goes open, shorts, or the resistance goes way up or down (or maybe just a little up or down if it's at the end of the valid resistances), the resistance is out of the range the module can learn, so it never will. That prevents someone from simply removing the connector and being able to relearn infinite ohms.

I kindda explained that in the post above (3 minutes before yours) :)

If the cylinder goes open, shorts, or the resistance goes way up or down (or maybe just a little up or down if it's at the end of the valid resistances), the resistance is out of the range the module can learn, so it never will. That prevents someone from simply removing the connector and being able to relearn infinite ohms.

Yeah the resistance and the resulting voltage sent to the PCM has to be with a certain range. So if his ignition cylinder is bad, the resistor bypass might be the fix. But what I was saying is even if the resistance is within proper range the PCM might not relearn the password if it hasn't been reprogrammed for the different car VIN. if he has a short or open in the wiring, then that's a separate problem he has to find.

Well since he's going to be getting at the passlock wires this webpage has some tips to check the circuit:

http://free-auto-repair-advice.blogspot.com/2008/05/diagnosing-and-fixing-gm-anti-theft.html

No we have not conluded that scanner he used was incorrect. I will try contacting him.
Yes i do understand what you're saying, but i didn't before. Unfortunately my limited experience with electrical stops me from being able to think it through completely, but it makes sense. I will rule out the scanner problem before going ahead with the bypass.
Also, by fixed resistor value.. do you mean basically pick a resitor value between 3k & 5k out of a hat?! I'm obviously a little confused. I thought i should leave ignition on run, and proceed to measure the resistance value, and replace with a resistor within ~5% of that value.

This is if the system is working and you want a resister that will work without recalibration. Make sure you read the cardone link this takes three times to recalibrate not once an alarm man told me he has had to redo more than once. He also installs resistors.
I would try a terminal tool and pull the wire suggested in the car forums link. If it starts buy a resistor install it and recalibrate,
http://www.tooltopia.com/ Lis 56500 these are in some parts stores. I don't recommend cutting a harness unless required.
As you could have 3 or more problems a new switch was installed in the past,corrosion in the harness,grounds in this wire,or calibration wasn't done correctly or possible other problems.

No we have not conluded that scanner he used was incorrect. I will try contacting him.

In early posts, based on the info you gave about the scanner it was incorrect. Like I said earlier, there's only 2-ways to reprogram this PCM, with a Tech2 scanner or a Mastertech (it's pretty clear the scanner wasn't one of these) hooked to a laptop. Or with a Passthru device hook to a laptop. If the guy had a Passthru device it would've programmed.



Yes i do understand what you're saying, but i didn't before. Unfortunately my limited experience with electrical stops me from being able to think it through completely, but it makes sense. I will rule out the scanner problem before going ahead with the bypass.


That's understandable. I think the scanner problem already has been ruled out. The thing is the the bypass probably won't fix your problem unless your problem is the ignition cylinder, then it would fix it. But I think your problem is probably a PCM that needs reprogrammed and probably a wiring problem on top of that.

Also, by fixed resistor value.. do you mean basically pick a resitor value between 3k & 5k out of a hat?!

What J-ri was explaining to you is how you would do it to completely bypass the ignition cylinder by unhooking the passlock wiring to the cylinder and replacing a fixed value resistor in the circuit.. Maybe he can clear that up for you.


I'm obviously a little confused. I thought i should leave ignition on run, and proceed to measure the resistance value, and replace with a resistor within ~5% of that value.

Well this is a different way of doing it. This way your passlock password value would be the same as original and the PCM wouldn't have to relearn-except that you have a different PCM in the car anyway so it would have to relearn the original password anyway. Also if your resistors are working in the cylinder so that you can measure the resistance, there's not much point in splicing in a resistor unless maybe you were trying to fix an intermitent ignition cylinder problem, but your probem isn't intermitent. So if you're going to do the bypass you could measure the resistance just to see, but after that it'd make more sense to just pick a resistor value in the range J-ri was explaining to you.

I hope that makes things clearer. Have you checked all the fuses?

I don't recommend cutting a harness unless required.
As you could have 3 or more problems a new switch was installed in the past,corrosion in the harness,grounds in this wire,or calibration wasn't done correctly or possible other problems.


I agree, cutting wires is not how I would go about it either. I wouldn't permanently install a resistor either, I'd replace the ignition cylinder if I found it was bad.

How I think he should go about doing it is backprobe the yellow and the black wire. Turn the key ON and measure resistance and voltage with a voltmeter to see where the resistance is at and if the circuit is functioning. If the resistance is in range, I'd conclude that the PCM should relearn the password following the 3 cycles procedure. If it's not relearning and starting, I'd look for a problem elsewhere. I would use that terminal removal tool to remove the black and yellow wires and stick a resistor across there to se if it will relearn. If it does, then I'd hook the wires back up and replace the ignition cylinder and do the relearn again.

I'm hearing you guys loud and clear. I just spoke to this fellow again, and he again stressed very clearly that he has used this tool quite a few times over the last several years on cavaliers. He says it has worked for all models from 95 up to about 2005-2006ish. I'm just repeating what he said to me, so take it as you will. I confirmed that it is in fact a snap on, and i explained to him that i was instructed many times that there are only 2 scanners that work, none of which are his. He disagreed.
I told him about the bypass, and he was adament it wouldnt work. "If the pcm doesnt see the key, it wont relearn"... i think he meant, the pcm is not communicating with the ignition, and wont relearn.

I dont understand first of all how the 3 cycle relearn process will work, if my anti-theft light doesnt go out!.. It doesnt go out after the ~10 minute period.

Also, just to be clear, i am using the original prom chip. Is'nt there a possibility that the vehicle will see this as the original pcm since this is the only memory storage device?

I'm hearing you guys loud and clear. I just spoke to this fellow again, and he again stressed very clearly that he has used this tool quite a few times over the last several years on cavaliers. He says it has worked for all models from 95 up to about 2005-2006ish. I'm just repeating what he said to me, so take it as you will. I confirmed that it is in fact a snap on, and i explained to him that i was instructed many times that there are only 2 scanners that work, none of which are his. He disagreed

This guy is feeding you a line of bull. Snap-ons cannot reprogram PCMs. The only way to program the PCM without the factory scanner is with a Passthru device and a laptop with GM software. Now, Snap-on makes a Passthru device but it's not a scanner and you still have to hook the passthru device to a laptop with GM software. If anyone else knows another way then they can chime in. So far it's just this guy saying he can program PCM with his snap-on. If this guy knows so much then ask yourself why he couldn't program your PCM. There's no reason he shouldn't have been able to if he had the proper equipment like he claims.

.

I told him about the bypass, and he was adament it wouldnt work. "If the pcm doesnt see the key, it wont relearn"... i think he meant, the pcm is not communicating with the ignition, and wont relearn.



Well going by what he said and not what he might have meant, this is just more proof this guy doesn't know much. Many people have bypassed the passlock. Now, if the PCM isn't communicating with the ignition cylinder then no it won't relearn. I've been saying this could be your problem. I posted a link earlier that instruct in how to check for voltage at the passlock.


I dont understand first of all how the 3 cycle relearn process will work, if my anti-theft light doesnt go out!.. It doesnt go out after the ~10 minute period.


As I said before, this is because you have a problem beyond what a passlock bypass will fix. Like a PCM that needs to be reprogrammed and/or a wiring problem. I suggested checking the fuses, and you said they are OK. You could try unhooking the battery and waiting awhile for any codes in the PCM to erase, then try to see if your theft light will go out. Next, you could check the theftlock's yellow and black wire as that link instucted.

Really, you're trying to fix an advanced level problem without the proper diagnostic equipment or service manuals. It just seems like you aren't actually digging into the theft circuit to find the problem and we're really just going around in circles


Also, just to be clear, i am using the original prom chip. Is'nt there a possibility that the vehicle will see this as the original pcm since this is the only memory storage device?

This is what I don't understand. If you have a '96 PCM, there should be no removable prom. The OBD2 PCM is basically sealed up on all the ones I've seen. If you could just remove proms no one would have to reprgram them. Maybe if you had a pic of this PCM and the chip you're removing it would help.

1)Now, if the PCM isn't communicating with the ignition cylinder then no it won't relearn. I've been saying this could be your problem. I posted a link earlier that instruct in how to check for voltage at the passlock.

2)As I said before, this is because you have a problem beyond what a passlock bypass will fix. Like a PCM that needs to be reprogrammed and/or a wiring problem. I suggested checking the fuses, and you said they are OK. You could try unhooking the battery and waiting awhile for any codes in the PCM to erase, then try to see if your theft light will go out. Next, you could check the theftlock's yellow and black wire as that link instucted.
Really, you're trying to fix an advanced level problem without the proper diagnostic equipment or service manuals. It just seems like you aren't actually digging into the theft circuit to find the problem and we're really just going around in circles

3)This is what I don't understand. If you have a '96 PCM, there should be no removable prom. The OBD2 PCM is basically sealed up on all the ones I've seen. If you could just remove proms no one would have to reprgram them. Maybe if you had a pic of this PCM and the chip you're removing it would help.

In response to 1) & 2):: I've got to be honest, i didnt understand before yesterday what you were saying, even though it is quite simple, and i didn't believe what you were saying was valid. I see what you are saying now. You have given me plenty of information to work with for right now, so this thread might need to take a break while i try these things. We are going in circles, first off because it took this long to understand, and also because the ridiculous weather condition here completely prohibits working on it. Check out the link i've posted that includes the pictures of the pcm, and of the outside conditions, (there was absolutely no snow 2 days ago, now look at it).

3) I've posted pics of the PCM.
Sorry for making you run in circles.
I'll have a question or 2 about pcms/reprogramming/relearning, once you have a look at the pcm i have.

http://s304.photobucket.com/albums/nn184/boomer_3_photos/96%20Cavalier/

3) I've posted pics of the PCM.
Sorry for making you run in circles.
I'll have a question or 2 about pcms/reprogramming/relearning, once you have a look at the pcm i have.

http://s304.photobucket.com/albums/nn184/boomer_3_photos/96%20Cavalier/

I think that is the knock sensor (KS) module, not the eprom. I should've been clear about that before. You do want to put your original KS module in the replacement PCM. This is not related to your passlock problem. The PCM still has to be reprogrammed. Try following some of the suggestion I gave earlier. Check fuses, unhook battery to clear codes and see if the theft light will turn off after cranking and waiting 10 mins with key ON. then check the passlock wiring, etc. I don't think you're going to make any headway till you reprogram the PCM whether you take the PCM and your VIN to someone who can do off-the-car reprogramming or buy a programmed PCM.

I think there was a recall on 95-96 Cavalier and sunfires because of this PCM corrosion problem. Maybe you could call a dealer or two and ask them about it. I think it wascampaign 98078. I'm not sure. But if they say they will fix it under the recall, maybe put the original PCM back in if you have it and tow it to the dealer. That'd be the cheapest way to fix it.

Why don't you ask your programmer what tool number he has {Snap On} Tool.
This way manic mechanic can go to http://www.snapon.com/ and look as the tool salesman sell J Kent Moore tools. Quit going in circles.
http://www.alldata.com/ They sell a years subscription for $29.95 and they have good electrical diagrams. From what I understand you cut a plug with appx.60 wires just splicing one wire to the wrong terminal plug will cause you many problems.
If a scrap yard has a good harness this might be the way to go on this job.

I do remote starters on the side- 96 J-cars have a "bulb-check" black wire that goes to the instrument cluster- this too must be activated only during crank- to avert a security light and start the car- so if you intent on bypassing the Passlock- look for this as part of your bypass plan...

Was instrument cluster replaced?