1991 Chevy Camaro 91 Camaro - engine will not turn on


Engine Mechanical problem
1991 Chevy Camaro 6 cyl Two Wheel Drive Automatic 156000 miles

I have a 91 camaro that will not turn on. This is my first Camaro so I am getting familiar with this GM product. I have extensive automotive repair experience but as I am not familiar with this particular model, I am hoping I can save some time with a point in the right direction.

This is what I know thus far: I recently bought this car cheap from the owner who claimed that there is an intermittent electrical? Mechanical? Problem. I drove this car for two weeks and thought that it drives very nice but just needed a tune-up. So I drove the car to a football game, came back after 45 minutes and the car would not start. It acted like it was just out of timing sequence. An occasional pop and a small backfire and then nothing.

Not being familiar with the car I went online looking for answers and I was lead astray by another online forum who obviously did not have a clue.

As I felt the engine needed a tuneup anyway, I went ahead and replaced the timing components, rebuilt the distributor, checked the compression, tested the fuel pressure, etc. In other words, I have eliminated any mechanical possibilities. My conclusion is that their is an anti-theft system involved with the ignition key or their is a short circuit in the wiring harness. After conferring with the local Chevy dealer repair. They confirmed the VATS and confirmed that part of the anitheft system is to turn off the injectors.

I have confirmed that the key pellet is good. I have confirmed that the two wires at the lock cylinder are good as I can get a reading down at the connector under the dash which is consistent with the ohms reading I get when I test the key.

This leads me to the next step which is to check the VATS module or possibly the wire or signal to the ECM.

I have done extensive research of this problem on the internet as I do not want to spend hundreds of dollars if there is a means to bypass the VATS system althogether. The dealership wants me to bring the car in but I don't feel I can justify paying 600.00 or more for Chevy's flaud engineering. I have read so many similar cases the last few days and I think this is a stupid system to have installed or designed. There should be a lot of frustrated people out there.

This is my first time dealing with this aspect of GM Engineering and I think it is absolutely ridiculous.

Is there a kit available to completely bypass the VATS module and allow the ECM to function without any hindrance. My son owns a 1990 Chevy Silverado pickup with a similar type engine except his vehicle does not employ the VATS and it runs reasonably well.

I will gladly make another donation if I receive a suitable answer to my question which helps me to satisfactorily resolve the problem. There are many answers out there which involve bypassing the pellet key and cylinder but I did not find anything regarding bypassing the VATS module altogether.

Access to wiring schematics and proven instructions would be great.

Do you
have the same problem?
Friday, January 2nd, 2009 AT 5:33 PM

1 Reply


Resistor sensing contacts are located in the Ignition Switch Lock cylinder. These contact the Key Resistor Pellet on the key when it is inserted. When the lock is rotated, battery voltage is applied through the ENG CNL Fuse to the PASS Key Decoder Module. The Pellet resistance is then compared against a digital reference resistance in the Module.
If the Key Pellet is the proper resistance, terminal A3 is grounded, energizing the Starter Enable Relay. At the same time, a signal is applied to terminal A2 to enable the Electronic Control Module (ECM). When this signal is received by the Electronic Control Module (ECM), it allows fuel injector pulses to begin.
If the Key Resistor Pellet is the wrong value, the PASS Key Decoder module will shut down for 2 to 4 minutes. During this interval there will be no output at terminals A3 or A2.
If the Ignition Switch is turned on again during this interval, the Timer will begin over again and the PASS Key Decoder Module will remain shut down for another 2 to 4 minutes. The PASS Key Decoder will continue the process even if a key with the correct pellet is used to turn the ignition back on. The Timer is restarted by the ignition voltage at terminal A1 when Ignition Switch is turned to RUN.
Once the Timer has completed its 2 to 4 minute cycle with the ignition off, the PASS Key Decoder Module and Timer are reset. A key having the correct code can then be used to start the engine.
The SECURITY Indicator is controlled directly by the PASS Key Decoder Module. If there is a PASS Key Decoder Module. If there is a PASS Key Failure this indicator will be grounded by the PASS Key Decoder Module with the ignition in RUN, BULB TEST or START. When the Ignition Switch is first placed in RUN, BULB TEST or START the Indicator lights for about 2 seconds as a bulb check. Thus, the SECURITY Indicator can be used to help diagnose the problem. For example, if the engine does not start and the SECURITY Indicator does not come on at all, then the contacts are not touching the resistor pellet on the key correctly. If the engine does not start and the SECURITY Indicator stays on, then there is a problem with the PASS Key Module. And finally, if the engine does not start and the SECURITY Indicator goes off after approximately 2 seconds, then there is a non PASS Key problem.

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Friday, January 2nd, 2009 AT 8:29 PM

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