Theft Deterrent System question

[LT4John]

My 96 LT4, 6 speed won’t start sometimes, but will if I leave it sit for a little while.



Over the last couple of months, my car would not start three times, each time all the lights come on the dash like normal but the starter will not turn and the car could not be push started. I looked at the wiring diagram and thought it was the theft deterrent system; it looked like the key lock was not reading the resister on my key. This system cuts out the starter circuit and also the fuel system which explains why I could not push start the car. Thinking this was the problem, I carried two sets of keys so when it happened again I could try a different key. This weekend it wouldn’t start again, so I tried a different key and it still would not crank. Again, I left the car sit for a while and tried it again and it started right up.



This problem is very hard to troubleshoot because when I go to work on it, the system is running again.



Question; is there a timer in the CCM which prevents the system from working if it thinks someone is trying to start the car without the key? OR am I wrong thinking my problem is with the VATS?

Any help would be great.
John

 

[Hrtbeat1]

Yours does sound like a VATS problem. Since the car starts after sitting for a while. If you take your key to a dealership they can tell you the "pellet" number (should be 1-15 IIRC) this corresponds to a resistor for the VATS system. Ecklers has a bypass for the VATS system ~$25 FWIW.


Yes the VATS system has a timer but I'm not sure if its part of the CCM. There is a parameter that can be changed in the ECM that will turn off the VATS.

 

[c4cruiser]

You can get a VATS bypass from the accessory catalogs that will effectively disable the VATS system.

The VATS system disables the ignition for around 3-5 minutes. If an attempt is made to start the car within that time, the timer resests itself.

The CCM (Centrol Control Module) controls the VATS system. If a key with an incorrect pellet resistor value is inserted with an attempt to start the car, the CCM will not send input to the Stater Enable Relay so the car will not start.

Have you checked for any error codes in the CCM? Do you have a "SYS" code flashing below the digital speedometer?

 

[LT4John]

Good stuff, c4cruiser and Hrtbeat1 thanks for the info. I will check next time to see if I have "sys" code flashing and will check the CCM for error codes. I will also order the VATS bypass from Ecklers.
This fourm and all the members are great!!

Thanks again,
John

 

[GeorgeT]

You may have a bad resistor in the key. If it's bad the car won't turn over, much less start. When this happens, the car "thinks" someone is trying to steal it and locks out the starter circuit for about five minutes to all keys, even the right one.

 

[jmccloud]

Vats

Crud in the tumblers will cause the VATS to trip.
My key was very rough to insert and extract. So, like a dummy, I shot graphite into the cylinder. Key slides like greased lightening.
A couple of weeks later, no start. Graphite on the key. Oh, crap.
Fortunately there was a set of foam ear plugs in the console so I 'cleaned it's ears' by stuffing the compressed ear plug into the key slot and drawing out a little less graphite each time. Got tired of doing that and found the time delay thing in the owners manual. So went and had a coffee.
1/2 hour later it started right up. A month or so later had to repeat the same rigeramole (my grandmother's term for a painful procedure).
I won't shoot graphite into the cylinder again, powdered teflon works much better.
Search VATS and find a table of values and where to put the resister. $1 or less at Radio Shack.
Good luck