GM Passlock Anti theft on a 96 Sunfire...Help?

[85 Cutlass Brougham]

My aunt has a 1996 Pontiac Sunfire convertible with a broken ignition lock cylinder in it. Unfortunately, it broke in the not quite off position and killed the battery. It will not rotate backwards to shut off fully, and now it is stuck in one spot and will not move in either direction. I have removed the lock cylinder from the car (it locked up totally afterwards), and managed to procure cylinders with keys from a 1999 Sunfire and a 1995 Sunfire. Unfortunately, the car also has GM's "Passlock" anti theft system built in to the lock cylinder and neither cylinder I have is exactly the same. However, from what I have read, the system uses an hall effect switch and it seems to have a magnetic pickup in the case and a magnet on the tumbler. Since I can probably change out the tumbler with one of the two good ones I pulled at the junkyard, will it still let the car start if the tumbler is from another car, but the case is from the original car? Is there another way to do a shade tree work around to this issue? My aunt has no money and no health insurance and can't work due to cancer treatment. I need to figure out how to get this thing working for her so she has basic transportation. I am hoping it will not need to have the computer reflashed when I am done, but I am afraid it might because of what I have heard from other people who have disconnected a battery on a 90's GM product. I will await answers until Thursday, when I make the 2 hour journey to try to fix this thing once again.

 

[82cutty]

Good luck! I have an 01 Impala that has a very intolerant Pass lock system. The history of the car is long.... The car has had the ignition lock replaced and the entire pass lock sytem replaced on several occasions. I had to have the BCM reflashed when anything was changed. It has to do with the vehicle and the VIN thru a computer sytem in Detroit. What I did was like hooking up a remote starter. You get the car started and then turn it off and take the ignition wire from the key and cut it and throw in a toggle switch. It will bypass the resistance part of the key and start the car. If you kill the battery or disconnect it you have to turn the switch off and do the whole thing over again. If you have a security light it will now always stay on. The Pass lock system measures resistance in the key when turning. My Impala has 3 keys and if you turn it to fast or to slow it will disableon all 3 keys. One trick I found is to either press the pedal a bazillion times with the key on or turn the key to the on position and let it sit from anywhere of 20 minutes to an hr then turn if off and then on again and try to start it. If you can try to have the original lock rebuilt/re-keyed to the original key. That might work or not, its tough to say. I had the lock on mine re-keyed and it 75/25 but I drive my car once every 2 to 3 months. Hope this helps!
Steve

 

[85 Cutlass Brougham]

Oddly, this system does not have a resistor built in to the key. This car uses Passlock I, while I think yours is variant 2 or 3, or it may be Passkey I, II, or III. It seems that Passlock was used in the cheaper cars like the Crapalier/Sunfire and the Grand Am/Clones while Passkey was used in the more expensive models and used the actual resistor. None of the keys I took out of junkyard cars seem to be GM keys, so I think the key uses a generic blank and the resistor or magnet on the tumbler is what is actually read by the computer. I will bring my DVOM with me Thursday to check this theory and see if I have figured it out. If the resistance is the same, then all this system senses is the reluctor passing by a magnetic pickup while the key is turned (the reluctor is not aligned with the pickup during run or start). If that is the case, I will just swap out the tumblers and keep the outer housing and pickup from the original part as I believe the tumbler is all that has failed. So, I may have found a work around for this less expensive system, but I don't know. I will post my findings if it works, or doesn't as I like to finish these tech posts so as to help others who may stumble on them through search engines.

Every time I work on a newer GM car, it makes me more and more content to own only low line Japanese cars when it comes to late models.It's amazing, but my 324,000 mile Nissan pizza delivery truck is still on it's original lock cylinder and key despite being started 20x a day for 11 years. This stupid Sunfire is not only hard to work on, but also low quality, thus ensuring the need for frequent repairs. Oh, and did I mention it is powered by a Quad 4...err 2.4 twin cam? Yes, because changing the name and adding 0.1 liters of displacement will make an unreliable engine reliable...

 

[custom442]

Can you rewire it to bypass the security system, or have you tried that already?

 

[85 Cutlass Brougham]

The computer needs both a signal from the ignition switch and a signal from the hall effect sensor to let the car run, so there is no easy way to work around it. There are things you can do involving relays, resistors and a voodoo witch doctor, but I am not ready to try that yet. What makes it more difficult is that the battery is deader than dead due to the car being left on for two weeks. I am afraid to change it out because of the volatile flash memory EPROM GM used during this time, but will bring my Cutlass battery and try to make a jumper to my truck to keep juice in it while I try to swap them out and do my proof of concept. Yes, this project is a spiraling vortex of GM electronic evil from the 1990's. GM level evil makes Joseph Lucas (the British Prince of Darkness) look like an angel of light by comparison.

If this does not work, the car will either end up at a GM dealer or I will end up buying a factory service manual for a 1996 J body. It's a 3-4 hour round trip for me to go there, so it's kinda like a NASA mission to repair the Hubble. You gotta try and plan it all out before you leave in order to use your time wisely.

 

[custom442]

Is the hall effect sensor a switch to supply the correct amount of voltage? Or does the computer/safety system need to read the original sensor? This is prob. a dumb question, but if the hall ef. sensor just supplies x voltage why wouldn't it be a splice and replace deal?

 

[85 Cutlass Brougham]

No, the hall effect sensor is like the magnetic pickup in a distributor. It senses rotary movement and is triggered by a variation in magnetic fields.http://en.wikipedia.org/wiki/Hall_effect

 

[custom442]

okay so from what I read, the hall effect sensor needs a ground, 12 v power/voltage wire, and the problem is supplying the correct amount of voltage to the sensors (which would be the other one or two wires on a GM?)

Is there some other circuit that operates the voltage pulsing besides just the magnetic sensor? Or is the sensor calibrated to each computer? ...I'm trying to understand why it's not a direct swap.

 

[85 Cutlass Brougham]

There are different resistances built into the varying sensors, and the sensors are staked to the body of the ignition lock. I am thinking that just changing out the tumbler portion of the lock while keeping the original outer body of the ignition lock will work. It comes apart pretty easily on the two I pulled from the junkyard today, and I think I figured out why the other cylinder will not move. The other issue is the dead battery, and if the computer will need to be reprogrammed entirely as I have heard it rumored, or if it will just need some sort of reset to the anti theft system, which I seem to have figured out how to do without a GM tech or special dealership tools. Supposedly, the leave it in run till it stops blinking the anti theft light then turn it off then start it method is supposed to work, but I have no idea if it will or not. I just wish she lived closer to me so that I could play with it a few times over a series of days rather than once a week for a few hours.

 

[85 Cutlass Brougham]

Well... I was wrong and my idea to interchange lock cylinder parts did not work. I wound up getting the original parts to work again and the car now runs fine. I jump started it, and the battery held a charge and did not require any dealer reprogramming. I just wanted to post a closure to this episode for anyone who may come across it in a Google search for this topic. I also got the A/C to work, degreased the engine, cut out the wet carpet (leaky convertible top) and punched a few drain holes in the floor pan to keep the wetness down.