GM Passlock 1 problem

I have a '96 Skylark with the Passlock 1 anti theft system. Occasionally, the system would malfunction, and the car would stall with the "theft" light on. I replaced the lock cylinder, which involved letting the system "relearn" the code from the new lock. The dealer said to start the car after installing the new lock. When the engine died, wait ten minutes, turn the key off, then back on for ten minutes, and repeat two more times. This worked, and the car started and ran fine, but when I shut it off, it would not restart and the theft light flashed again. In a service manual, I found another relearn procedure that said to try to start the car and when it died, wait ten minutes with the key still on until the theft light stopped flashing and then start the car. This worked fine and the car would restart, but if I wait ten minutes before restarting, it wont start. I then tried letting it run for ten minutes after first starting it, and this seemed to solve the problem. I could even wait overnight and it would still start. But then if I start it and shut it down and try it again a half an hour or so later, it malfunctions again. It's as if it keeps going back into the "relearn" mode. Any suggestions? I've been considering an exorcist....

I have a '96 Skylark with the Passlock 1 anti theft system. Occasionally, the system would malfunction, and the car would stall with the "theft" light on. I replaced the lock cylinder, which involved letting the system "relearn" the code from the new lock. The dealer said to start the car after installing the new lock. When the engine died, wait ten minutes, turn the key off, then back on for ten minutes, and repeat two more times. This worked, and the car started and ran fine, but when I shut it off, it would not restart and the theft light flashed again. In a service manual, I found another relearn procedure that said to try to start the car and when it died, wait ten minutes with the key still on until the theft light stopped flashing and then start the car. This worked fine and the car would restart, but if I wait ten minutes before restarting, it wont start. I then tried letting it run for ten minutes after first starting it, and this seemed to solve the problem. I could even wait overnight and it would still start. But then if I start it and shut it down and try it again a half an hour or so later, it malfunctions again. It's as if it keeps going back into the "relearn" mode. Any suggestions? I've been considering an exorcist....

Sounds like the BCM is going bad. Or, maybe it's your key(s). Have you tried a new key?

I have the same problem on my 96 Skylark. After a couple of years of reliable starting, my Skylark started flashing a "Theft Detection" light. Once the switch was turned off, sometimes it would re-start after a few tries, sometimes it would be weeks before it started again. The last couple of times it died, I had it towed to my local GM shop. In each case, it started fine once it got to the shop (I am wondering if the car being bounced around by the wrecker might have done something)? The mechanic hooked the diagnostic computer up to the vehicle and found no error codes being displayed. In each case, it malfunctioned again shortly after I got the vehicle home. The last trip to the garage cost me $200.00 for a reprogrammed key. The mechanic said the key might not be sending the correct code to the computer. My key does not have a chip on the key, so I am going to assume I might have been taken for a "ride".
Now, my instrument lights are no longer functioning either. I have checked every fuse in the vehicle (both in the dash and under the hood).
Does anyone have any idea what I might can do?. The last time I talked to the shop, they wanted to dismantle the dash and send it to Detroit for further troubleshooting. I would really like to avoid any more "blind guesses" from the shop. Any ideas would be greatly appreciated. Thanks

Shiftman...I did get mine fixed. The problem ended up being the instrument panel cluster. You are correct that this vehicle does not have a chip in the key if it is a 1996 Skylark - It should have the "Passlock 1" system rather than the "VATS" or "Passkey" systems. The resistor and a switching assembly are built into the lock cylinder. $200 would however be a very reasonable price if they replaced the lock cylinder and reprogrammed the system to accept it, as the lock is very expensive. With a problem such as this, replacing the lock would be the most logical first step, so they may not actually be trying to "take you for a ride".
When the theft system shut mine down, I would get a code 1629 (theft fuel enable - incorrect / no signal).
The next time it fails and the theft light starts flashing, leave the key on until the light stops flashing (approx. 10 minutes...). Then start the engine. Light should stay on for a few seconds, then go out as it is relearning either the IPC or the lock cylinder. You should then be able to drive it...
When you say that your instrument lights are not working, do you mean the indicators or the illumination lamps?
If you do end up having to replace the IPC, don't be surprised if you are quoted around $800 for a new one. I got lucky and found one from a salvage yard with only 10,000 miles on the clock for a couple hundred bucks.

Here is a description of how it works - maybe it will be of help for you or your mechanic...
1. When the lock is turned to "ON", the lock is sending the resistance signal to the Theft Decoder Module (built into the IPC), but the module is not yet looking for it.
2. When the lock is turned to "START", the ignition switch grounds the "bulb check' wire to the IPC which activates a time window that the module expects to see the signal from the lock.
3. When the engine starts and the key is released to the "RUN" position, the lock resistance is sent to the module.
4. When the module is satisfied with the resistance from the lock (and the timing of its delivery...), the module then sends its password via the data bus to the PCM that all is OK and the vehicle keeps on running.

Note that the resistance cannot be present while the vehicle is cranking - only immediately afterward.

So the main possibilities are: 1. Bad lock cylinder. 2. Bad ignition switch. 3. Bad IPC. 4. Bad ECM. 5. Wiring problem to either of these components.

Hope this helps.

"When you say that your instrument lights are not working, do you mean the indicators or the illumination lamps?"

I am not sure that I understand what you mean. What I meant was the whole array of "Idiot lights" has quit working, including the one that flashed a "Theft Detection" warning. These are the ones that light up when the engine is first started, but then go off, only mine have now stopped illuminating at all.

I took a look at my keylock and it appears to look new (no scratches from trying to get the key into the slot), so maybe I was mistaken about what was done. I do know that if a new keylock was installed, I never got new keys. I am still using the original keys. This strikes me as odd because the last time I bought a new keylock for my Ford truck, it came with new keys.
At any rate, I will have to take it to another shop if I can get it started, maybe this shop will get it propoerly diagnosed. I have no clue as to what an IPC is. Can you explain?...Thanks

Sounds like the passlock sensor was replaced. This is a fairly common diagnosis for your problem. The most likely problen is actually a faulty instrument panel cluster (IPC). The brain for the security system is there...

You will need to remove the cluster and send it out to a Delco repair facility. "They" may only accept it if it is sent by a GM dealer.

Good luck!

The reason that I was not sure about the lock cylinder is because this one has no scratch marks on it like you would find on cars of this age. My other vehicles have scratch marks from hitting them with the key before the key finds its way into the hole. The one thing that I am sure of is that I was issued no new keys.
Can you or anyone else tell me where this IPC is located?
Are you talking about the main clustwer where the gauges and lamps are located?

Shiftman...The IPC is the Instrument Panel Cluster, wich includes all your gauges. Also, the lock cylinder for these does not come with new keys...When you purchase the new cylinder, the dealer "codes" the lock to your old key.

I emailed a place in Indiana that advertises for diagnosing and repairing IPC problems. They emailed me aphone number and asked that I phone them. I am curious as to their shop charges for diagnosing and repairing the problem. I can then do a cost comparison for letting yet another dealership try and repair it. Thanks for the response.

UPDATE: I contacted Southern Electronics in Virginia about my problem. They sent me a replacement cluster (set at my correct odometer reading) for my Buick and a prepaid shipping box for me to send them my old one. The new cluster fixed my problem and the bill was only $200.00
Hopefully, this info might help someone else. Thanks to all that replied.

Ok, I have a 1996 Buick Skylark that I bought in December of 2003. My parents test drove it for me for about 25 days, before they brought it to me. I drove the car for two weeks when the change oil light came on, I drove it two maybe three miles, when the car stalled on me. That was the first of Feburary. The car has not started since. It was two quarts low on oil, but I do not think that would make the engine lock up. I noticed the day after it stalled on me that the anti-theft system light was lite when I would turn the key over. all my gauges work, all my lights work, everything works, but when you turn the key over it makes a weird beep/hum from around the starter. It does not try to turn over, or anything. Could this be the same problem you had? I would rather try to fix the theft system then to try and install a new engine. any information you can give to me would be greatly appreciated. Thank you in advance for any time and assistance you can give to me.


UPDATE: I contacted Southern Electronics in Virginia about my problem. They sent me a replacement cluster (set at my correct odometer reading) for my Buick and a prepaid shipping box for me to send them my old one. The new cluster fixed my problem and the bill was only $200.00
Hopefully, this info might help someone else. Thanks to all that replied.

The brains of the ignition system is located in a chip located on the back side of the instrument panel. When my theft detection system would activate, the engine would start for about 2 seconds then shut down. The fuel system was not supplying fuel to the engine because the theft detection system was giving an indication that the car was being stolen.
I would suggest you give Southern Electronics a call and ask to speak to a technician. These folks were very helpful in fixing my Skylark. I have not had any issues with it since I replaced the instrument panel.

shiftman - I have the same issue with my '96 !! Sounds like a recall should be in order!

shiftman - I went to my friendly GM dealer and when I asked about this issue they told me that when they replace the ignition switch they set the tumblers to match the existing key. I don't know why; I guess it's easier that way.

BTW, I am about to drop $80 for a new decoder (GM calls it the ignition switch - I hope I have the right part, it's a little plastic and electronic device that fits around the key tumbler....which I thought was the ignition switch. I am confused.

On my Intrigue, it cranks but won't start - when it acts up. Other times it starts after a second try, other times it starts like normal. Is this similar to everyone else's abnormal behavior?

I found out simple way to disable the passlock1 prmanently. I did it on my Cavalier 96 and it works so far.
You can use it if ocasionally you are still able to start your car. All you need to do is to start the car (with your semidefective passlock sensor), and then disconnect the three wires plug (wires that run from the lock cylinder to the instrument panel) from the instrument panel while engine is running.
Engine will start the next time without any passlock "authorization", but "theft system'" light will stay on. If you do not like it, you can remove LED from the instrument cluster board.
I am not shure if the disablement will work after battery gets disconnected. Possible, that you may repeat it all over.

hey all i dont have a buikc but i have a 98 achieva and it is passlock 1 and it has thisproblem we replaced the ign lock switch because the dealer said ti was bad, but to no avail

never see a security light or anything except for once after i unplugged the PCM or BCM or whichever controlmodule it is up on the firewall in the cowl, and then i could leave the key on til the security light quit blinking and then the car was great for about two weeks after that and now it will not start again, it will jut immediately after firing up,

the cluster is fubar all the indicator lights and guages are screwy all over the place and the speedo even, and the headlight indicator is always blinking,

also the shifter is really hardot get out of park, its a real big struggle/fight

car will run awesome, when it will start, likea new car

at only 80k miles

i sent an email to southern electronics a bit ago and told them al about it and that i needed to send this IPC in to them and that i removed it again and its ready to go

i had removed it a couple weeks ago to clean all the contacts with electric contact spray, at the same time i unplugged the BCM or PCM and then got the blinking security light for the first and only time


what a mess

also if you replace the passlock key switch with a new one you dont have to have the dealer program the car to the new one do you ?? i was otld there are about 6 different ones, 6 different resistances they used