97 blazer 4.3w timing

Now that those ground wires are off of the alternator and the red wire is attached, do you have lights, starter etc?

IIRC that eyelet connects to one of the thermostat bolts and again, IIRC the ECT and PCM grounds there. Flash it across ground and see if there's any spark, if not, connect the eyelet to ground.

When those wires are off the post on the back of the alternator they are dead as well as all power to the system. I checked my 98 s-10 it does not have those two wires to the alternator. They both come out of the big wiring harness just behind the coil.

The black 16ga wire and blue 12ga wire both attach to the alternator with the red wire. They are both fuse links. The way they were connected originally is correct.

Here are some tests:

1) Disconnect the battery negative terminal from the battery.

2) Disconnect the 32 pin connector from the VCM (connector C3).

3) Disconnect the ECT and TPS sensors.

4) Measure the resistance from pin #4 in the VCM harness connector, (black wire) to the black wire at the ECT harness connector.

5) Measure the resistance from pin #4 in the VCM harness connector, (black wire) to the black wire at the TPS harness connector.

6) Measure the resistance on the black wire from the ECT harness connector to the black wire in the TPS harness connector.

Post the readings for each step.

All show .3 ohms

Did you check grounds Right Radiator,Below water pump,and Right front frame?

yes I have taken them loose and cleaned them all I could find. all wires appeared good not green or frayed.

Have you physically looked at the PCM? Believe it is located in the air box......would not be surprised if you found that rodents ate some the wire harness to the PCM.....

the computer is on the passanger side just on top of the coolant resavor. Nothing is in the air box ?

All show .3 ohms

Excellent.

Disconnect the positive battery cable.
Reconnect the negative battery cable and tighten it up.
Disconnect C1 at the VCM, (pretty sure it's the blue connector).
Measure resistance from pin #23, black with a white trace wire to battery negative.

Any friends have a GM vehicle that you could swap alternators and check this item out.
A good alternator rebuilder could check it for you. Don't trust parts store checkers.

The reading there was .2

I have a 98 s-10 not sure both alternators are the same my s-10 is base this blazer has full power even the compass and fancy stuff.

.2 ohms is good BTW.

On the techII, did you show 25.5 volts on "ignition 1" with the ignition on position and the engine off? If so, the alternator can't be the problem. Easy way to check is take the alternator out of the equation by disconnecting the red wire from the back of it and check on the TechII again.

Do you know any history on this vehicle? 1997 had a boat load of issues with the ignition switch causing all kinds of seemingly non-related stuff to happen? Do you know if it's been replaced?

No I don't know any history other than what the guy told my son, I talk to my son today he is going to ask the guy if he know about anything replaced. My son lives in North carolina he paints cars and trucks for a few race teams down there in the Charlotte area. This guy works next build over from him and thats how he knew about it. my nephew was there and had room on his car hauler to bring it up to me. I had to replace the ignition switch on my 03 impala it was causing the heater not to work figure that one. I think it is something with in the vcm that is telling the tech II about the voltage, that might have also something to do with the 1621 code.

When you remove the red wire all power is shut off, so the tech II has nothing to read.

I know, I keep thinking about that P1621 and am reluctant to suggest replacing the VCM for several reasons, main one being those things are just about bullet proof and rarely fail. That's why we're spending so much time on grounds but, the ignition switch could cause that stuff too, and it's a ton cheaper than the VCM.

I know all the sensor grounds go to the VCM but is there a block that they all go to to become one wire. Do you have anything showing all the gound locations to see maybe I have missed one. Yes the ignition switch is a real possibility but it just seems like an open ground some place.

You've checked all of the grounds, and the continuity of the ground wires and they all came back fine. All of those tests included ground splices & body grounds. I'm convinced it's not an external ground problem. If it's in fact a ground problem, it's gotta be in the VCM. Some of the ground tests I had you make checked the ones that can be easily checked without taking the VCM apart.

Just for grins, reconnect everything and write down the DTC's in the order they spit out. Then clear the memories, turn the ignition off for 30 seconds, turn it back on and see what DTC's reappear. Write them down in the order the are retrieved.

I cannot clear any codes I have tried to clear them, they stay in place. I have cleared codes before on other vehicles and it always took a few cycles for them to return but these cannot be cleared.

When you send the command to clear, does the TechII confirm that the command was sent?

I will need to go do it again to confirm that.

This is the ignition switch and it runs about $100. Not difficult to replace, takes about an hour if you haven't done one before.

http://i561.photobucket.com/albums/ss58/cwhook/97ignswitch.png

Most all of them fail at some point in time, some sooner than others. I suppose you could call it "preventive maintenance" or being "proactive" by replacing it ;) For what it's worth, it's an educated guess.

Yes it says it is clearing codes and it did clear two of them, both ECT codes and the 1621 code. But when I started the engine again they came right back. The p0118, p1115, and the 1621 code cleared but came back.

I would rotate the engine until the timing mark is close to the bottom. Use a socket and 1/2 ratchet rotate counter clock wise until its on TDC. Pull the distributor cap and mark the rotor. Have somebody watch the rotor. Turn clock wise until the rotor just starts to move. Stop at this point post what the reading is if over 20 degrees think about a two piece timing set. I've had many over 30 degrees and they will set many codes as the computer is hunting. They also won't run properly which is your main problem.

Reading all this it seems a piece of the puzzle is missing here, there may be something in the recent history of this truck the prior owner is not telling you, you should have tracked down the source of this by now, based on all the advice, possible a mismatched component has be replaced and has skewed all the diagnostics. The scanner readings are inconsistent with any normal inputs.

Old Master found a topic that does make sense, it is about the ignition switch. In almost every case from those who had much simular problems as I am having. Replacing the ignition switch fixed the problem, ignition 1 which is part of the switch is showing 25.5 volts. I have a 2003 implala the heater and other things where not working, a GM mechanic said as crazy as it sounds replace the ignition switch. I did it working fine this was a year ago,so thses days nothng seems to be always as it is.
The timing is right on now showing the right numbers on the scanner, when this truck was first worked on by my son after he got it he had a friend use a small scanner that told him the 118 code and the 123 code so he replaced the ECT and the TPS.
So before replacing the VCM i will try the ignition switch the chance of it being bad are far greater than the VCM. I will post the good, the bad or the ugly once I get it installed I hope to have time tonight.

With your voltage reading some people with large stereo's install two twelve volt battery. If hooked up wrong you would get around 25.2 volts. I still agree with Max Wedge something has been changed.

yes all parts have been replaced all with ac delco or delphi. It does look like the vcm has been off before from the marks on the clips. I contacted a friend of mine at a dealership gave him my vin and it is the right numbers for that vin. The other thing that can cause high voltage in these sensors and the system voltage is an open ground all have been cleaned and check for resistance. So just another step in this process but I am open to new ideas tell me what you would do and i am willing to try it.

http://wiki.answers.com/Q/Why_doesn't_a_transformer_work_on_a (http://wiki.answers.com/Q/Why_doesn%27t_a_transformer_work_on_a) DC_supply
On a coil the negative is grounded each time the coil is fired. This is why you can watch a test light blink on a negative ground on the coil.
Use your DVOM and check for a AC on your battery from a bad alternator or battery charger. Normally a bad ignition switch will have low voltage or no voltage not double voltage. I don't think Old Master believes your readings.
Note the link takes you to the site click on the complete question.

Thanks for your post but both Old master and I are searching for a cause to those readings. This vehichle has been a major pain in the butt so it is worth the try on my part. I got it half way done last night but had company decide to visit so i did not get to put it back together.
But you post is interesting because I have had to charge the battery often be it has not been run very much, and many times it was crank the motor with a no start so that would run ther battery down. Once I began using a tech II scanner is when the info on the 25.5 volts on data 1 engine came to light. I hook the tech II up on my 98 S-10 and it reads 12.8 on dats 1 engine 1, so something is wrong in the blazers system.
If the swicth does not fix it then I guess the next step is to replace the VCM, but I still do not think it is the problem. Computers store info good or bad some thing has told the computer that the sensors and the voltage is high the question is what. As I said I am open to preforming any and all tests please tell me what tests you would do if you were working on this blazer.

I would check the voltage on my battery charger. I would swap alternators on your vehicles if possible and check the alternator for A-C voltage. Think scrap yard CPU as if it don't work they will exchange it or refund within 10 days. Try cleaning all computer connections with contact cleaner. I assume you purchased a new ignition switch.
Use your DVOM and verify voltage the tech11 is giving you.
I'm retired but GM computers used to have an E Prom I would check this number and look for a bent pin. It plugs in in the back of the computer.

Again none of the info coming out of that pcm makes any sense, especially the 25v readings, no way that can be accurate. I would try and get another pcm just for test purposes.

No change with the new switch but no big loss the old will fit my s-10 if I should need one. The alternator on my s-10 is different than the one on the blazer. I have check the alternator is is ok so next step is the vcm. I called a company here in Ohio I was told about by a friend of mine some time back, they sell used VCM's they test them but do not refuerfish them. I talked with a guy there my friend says knows what he is doing and told him all I have done and what codes and readings. His first question was has it been off the car before and could I see any pry marks on the clip and yes they were pry marks. So for 90 dollars shipping included and gave him my vin so he could do the flash program I bought it. So next week when i get it the tale continues hope it has a good ending.

If you remove all of the wires from the terminal on the back of the alternator, clamp them all together with a vice grip, (insulate it with a rag etc, so it doesn't short out) you can start the engine and check voltage on IGN 1. You'll only show ~12 volts for battery voltage, but that will tell if the alternator is causing the funky 25.5 volt reading.

I took the alternator to a shop that I trust they checked it and it is fine, the guy where I am buying the VCM said with a 1621 code and the high voltage to the sensors the VCm has issues. At this point there is no other reason for the codes and the problems all others have been checked and double checked. I have already got to deep into it not to finish it and fix it.

I was a tech for several years before ASE was even a dream, and if this VCM is bad, IIRC it will be the third one. Let us all know what happens. This thread has quite the following.

Rodney told me that to find a bad VCM is rare, when he buys them mostly just need to clean them up. But at this point I don't know what else to try, I have cleaned every ground, taken apart all connectors in the wiring harness checked them. The 1621 code and the system voltage code that will not clear are 2 very important negatives that only come from the VCM. But how did they get there, what caused them is an unknown. I trully belive that this vehicle has not been run in a long time, along with the evidence I have seen about plastic ties on places that are not factory. Serious pry marks on the clips to the computer telling me it has been work on or removed at some point. I hooked the tech II to my S-10 and my denali and it gives good info so I know the tech II is good. Rodney asjk me a few questions one much like Old master ask what happens if I clear the codes. Only the codes related to the ECT clear but come back as soon as I start the motor again. That ties to the 1621 code about the long term memory preformance, you can fix the problem but you cannot get the computer to see it is fixed. It will not accept info from those sensors now it is locked in it that they are operating at a wide open throttle position. The VCM Rodney is sending is programed for my vin and I will use nothing from this VCM on the new one. 90 more dollars after what I have put in it to this point is worth it to me. Again I am open to any suggestions of things to try and will welcome any and all.

Way back, I don't know how many posts ago, when you checked the ground to the PCM, the comment was made that the PCM is getting ground, what happens to it once inside the PCM...who knows. If the new PCM fixes the problem, I guess we know what happens... it goes haywire! Got my fingers crossed ;)

Mine will be crossed also, if I had hair it would have already pulled it out. The main thing the guy said to me was if you cannot clear a code the VCM memory will hold that code and will preform as if that is still a condition. He said when you clear a code using a tech II it should not appear until it is seen again by the computer whan you start the motor or try to start the motor. Now if he was just telling what i wanted hear then it worked, but they sell many of these computers for all types of cars every day. Hope it does it, I will know next week unless they got it shipped today but even then with all the packages in every system next week is my bet. I did break off the damn hazard switch when putting it back together.

Way back, I don't know how many posts ago, when you checked the ground to the PCM, the comment was made that the PCM is getting ground, what happens to it once inside the PCM...who knows. If the new PCM fixes the problem, I guess we know what happens... it goes haywire! Got my fingers crossed ;)
While the PCM is out use your ohm meter and check that the ground is good from the engine ground to the PCM. You may have to use a small gem clip to insert into the harness without a breakout box. One end on clip other on good ground.
23 blk/wht
22 on older manual watch color.

Using the info from a gm shop manual for a 1997 S/T truck I traced each ground wire going into the VCM and all tests show that the ground is coming to the VCM. Like Old master just posted a few posts ago what happens to it once it gets inside is any bodies guess.

Happy days are here again YE HA UPS brought the VCM I ordered yesterday and I installed it and she purrs like a kitten. It has been running for about 15 mins all readings on the tech II are good. So in this case it was a bad VCM, what caused it to go bad is not known by me but the good news is it running fine.
I want to say thanks to all who shared their thoughts and knowledge with me, and special thanks to Old master for all his help.
So merry Christmas to all and to all a good night.

FANTASTIC! That's great news! Nice job sticking with it, some people would have given up a long time ago. Thanks for posting back.

I have never been a person to let anything beat me, some times it costs me more than it should. I drove it about 20 miles had the tech II hooked up my son in law looked at it while we were driving, all is good no codes all data with in the range. The old one had tranny codes and abs codes but nothing has come up on this one, it shifts clean passing gear works.
I think the key to the fact that the VCM was bad is that I was not able to clear codes with a tech II, even just enough before it would start. Much like a virus in a laptop once there it stays and will effect the laptop preformance.

Thought so, everything pointed to that or a ground, good deal, nice to have it back online!!

I'm glad you got the job done and didn't give up.