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Passlock I and II Disablement



This worked great on my 2002 Alero. I used it for permanent disablement and did not install a remote starter. The original bulletin is from GM Engineering and is written for GM Trucks and Vans. Following the link is a rewrite of the same bulletin so that it can be applied to GM cars with Passlock I or II. Hope this helps some of you with Passlock problems!


The following is a procedure to disable Passlock I or II Systems for vehicles in which remote start/stop system installations are required. This procedure is required because a remote start system will not function with the current Theft Deterrent System (Passlock) which is included on many 1996 and up GM vehicles.

Please note that this modification is intended to be used only in conjunction with the installation of a remote start/stop system and does not provide a procedure to install a remote start/stop system.

If an attempt is made to start a vehicle by a means other than a key rotation in the ignition switch, the Body Control Module (BCM) will interpret this start as a vehicle theft and disable the fuel injectors.

A minor wiring modification may be made to allow the vehicle to be started remotely. This modification includes adding a switch to allow the customer to select “ON” to allow remote starting or “OFF” for normal Passlock operation.

CAUTION: When this modification is performed and the switch is set to the ON position, the theft deterrent feature will be disabled. When the theft
deterrent is disabled the SECURITY/THEFT SYSTEM telltale will light up indicating that the theft deterrent system is NOT functioning.

Refer to appropriate GM service manuals and/or SVMQP Electrical Guideline Manual for instruction on splicing and electrical connections.
1. Select a suitable on-off switch (see note below) which will be used to disable/
enable the Passlock System. Mount the switch in a location such that it is
accessible to the driver and will not interfere with normal vehicle operation.
NOTE: This is an extremely low current circuit (approx. 7mA), it is therefore very important that a high quality, low energy, fast acting switch be utilized
for this application.
2. Turn the ignition switch to the OFF position.
3. Locate the Main Ignition Switch Harness in the Column. GM's Passlock System wires exit the Ignition Switch Tumbler together and then join with the Main Ignition Switch Harness. (See http://www.bulldogsecurity.com/ or and select your Make, Model and Year for wire colors and clues on the quickest way to access these wires.)
4. Locate the Yellow Passlock Data Wire which is included in a bundle of three tiny (20 GA) wires wrapped in friction tape.
Cut this wire and splice a 0.5mm2 (20 GA) yellow wire to each end of the cut wire.
Keep wire length to a minimum. Route modification wires clear of moving parts.
Connect the yellow wires to the switch such that the contacts are OPEN when the switch is in the ON position.
5. Turn modification switch to the OFF postion (contacts closed).
6. Start vehicle to verify normal operation. If engine “cranks but will not start"
recheck the switch position (contacts should be closed), wire connectors and
modification wiring.


To enable remote start:
Start the engine with the ignition key (modification switch must be in the OFF
position). Turn modification switch to the ON position (contacts open). The
SECURITY/THEFT SYSTEM Telltale will light up indicating that the Passlock System is inoperative.
Once the SECURITY/THEFT SYSTEM telltale has been on for at least 5 seconds the vehicle can be turned off and then remotely started.

To disable remote start:
The Passlock System can be reactivated by turning the modification switch OFF
(contacts closed). Vehicle can either be running or off when this is done.

Please note that the VCM/PCM will record Diagnostic Trouble Codes (DTCs) related to the security system when the modification switch is in the ON position (circuit open). This is due to the way that the VCM/PCM interprets this condition.

Any condition which removes battery power from the Vehicle Control Module/Powertrain Control Module (VCM/PCM) (e.g. dead battery, disconnected harness connectors, etc.) will prevent the vehicle from being restarted. If the engine exhibits a “cranks but will not start” symptom, place the modification switch in the OFF (contacts closed) position. This will reactivate the Passlock System and allow the vehicle to be started with the ignition key.


Proud Member of The Anti-Passlock Club:thumbsup:



Hi Anyone,

I am the unlucky person who hired someone to install a remote start Viper Alarm in my 1988 Trans Am [GTA] with TunePort Fuel injection. The vehicle quit starting with the remote and later quit starting with the key gradually. I called the "expert" who installed this & he was not very helpful, suggested I take it to a GM dealer after he removed alarm from system leaving a myrid of disconnected hanging wires that do not match. It is exhibiting the syptoms described here, "cranks but will not start" except mine does not crank most of the time but when it does crank it will start. If I jumper the starter wires it will "crank but not start".

All mechanical devices are OK, ie Starter, Battery, etc...

My question: How I can bypass this mess and supply all power needed to make it run like it should?

I know it needs power for:

A) Starter relay under dash - YES
B) Fuel Pump relay - YES
C) Distributor - YES [is there a relay here]
D) Fuel injectors - NO [is there a relay here]

Anything else?

Gary D.

My son has a 1996 Pontiac Grand AM with the same Passlock situation. Light comes on. Car will not start. Rotate the key over and over and wait is out and it may finally start. Our mechanic would not touch it. No recourse but to send my son to the dealership. Obviously not in retrospect a good move. $500 to replace some part under the hood. Son came to pickup car and light still came on. They said needed to send instrument panel component away to be reworked and or calibrated for $300 more. Son came to pick up car, drove away and light came on, came back they reset it, drove to gas station and car would not start. Took it back and they gave him a loaner car. ( now that is amazing.) Sent the part away again. 4 more days. Came back and they called. Light still on. Said car needs another part in the system for only another $175 no labor will be charged. They installed the part. Light still on. Now they say they will send the part(s) away again. Dealer contends that it is a chain affect that a new part installation throws off the other components and required recalibration. Son still has loaner car. Son told the service team leader about all of the many Passlock complaint web pages and the referenced GM service bulletins. They say they never heard of them before and seemed uninterested. At this point the Grand AM which has 117K on it is still in their possession. Did you ever successfully install the $5 on/off toggle switch that was the referenced solution in your column on the forum page? Inquiring minds want to know.


I have a 1999 grand am like others mine acts as if it's not getting enough gas figured out it's the passlock system not the fuel pump i allready paid 500.00 to replace. I tryed to resent the passlock but my security light stays on. which apartly means the lock and cylinder are bad? Just wondering if it's best to replace them or is there away to disable the theft system or by pass it to get it to work? will the toggle switch work in this case maybe? thanks for any advise


New member
Ok, first update;

I removed the steering column covers and after a brief confusion found that the three wires from my key cylinder to the Theft Deterrent Module are molded together, one outside and the center wire are black, the other outside is white. Not yellow as described in the instructions above.

So I took a chance and pulled the wire molding apart as carefully as I could, cut the white wire and wire nutted the switch to it for testing. Apparent success so I installed spade connectors to the white wire and two yellow 18 ga wires to the ON/OFF switch I bought. Installed the switch down on the side of the center console.

So far, so good. If there are any further problems I'll post again. Otherwise, this seems to be a good fix for starting the car when the theft deterrent module acts up. Hopefully this will help other members in the future as it has helped me.



Staff member
Thanks for the update
Just for advice= when dealing with GM Mechanics & especially - "Service writers' ask them for the GM service teck rep's phone #!! There is many reps available to them by phone!! Most never use them - believeing "the dealers /mechanix know it all!! In my many years = ive found the teck reps dont know it all either!! yet when theyre sitting in their offices -the teck's will all talk about their weird problems- then one will say -i had that happen in Bum___k area!! the fix is this!!!!!!!!! believe me -this happens -then they will call!!


New member

:)I put a different pcm in because old didn't work right. I had to relearn it. I did it by the key thing. Instead of turning the key all the way on I turned it until lights in the panel came on. Then wait until the theft light goes out. Then turn the key to start not back and it works just fine. Mines a 1996 grand am se


New member
Ok, I have another update with the Theft Sys saga on my '96 Grand Am. After installing the switch, it seemed to work out but then .... yes, the Theft Sys light started flashing, the switch didn't help no matter the position.

I happened to be talking to a tow truck driver, the subject came up and he's had a similar issue. He said he just grounded out the security module.

So I pulled the wires from the switch, tied them back together and reconnected them to one side of the switch, then wired the other side to ground. Now, when the switch is open, the theft system circuit is closed as is normal. If there is a problem, flip the switch and the theft system circuit is grounded out.

I have been driving it now for a few days and have not been able to make the car stall out with the theft system since.

Ah, sweet success!


Staff member
very interesting solution

Ed Plogger

New member
I am definitely needing help with the passlock on my 1996 grand am. You hear and read so many things that it gets severely confusing. I'm going to try the 2.2k resistor but I have a question. Does the black wire get cut into or just stripped back to solder the resistor in place? Also, I only read 10.8 volts on the white wire and 1.8 volts on the yellow wire. Is this ok or should I have 12 v and 5 v on those wires? Please let me know. I am about ready to find a book of matches for this thing. Signed desperate in Asheboro.


Which set of instructions are you referring to, something in this thread or somewhere else?
Thanks for asking. I have been feferring to various bypass instructions from other sites. I guess I need to get it narrowed down to the actual correct procedure for a 1996 grand am. I also would like to know where my voltage drop is coming from on the white 10.8v and yellow 1.8v signal wire. Specifically what wires to check for poor connection to the cluster. I changed the cluster and still get the same voltage so yeah I think it has to be wiring related now. However, I am not an expert and I really can't afford to put it in the shop. If I get good instructions, I'm usually pretty successful. Thanks


Staff member
None of the various bypass instructions mention anything about measuring voltage. They all instruct to cut the yellow wire and measure the resistance from the key end of the yellow wire to the black wire and then insert a resistor with that ohms value.
Why are you measuring voltage?