HELP----Still need help, left at dealership while on vacation. they reflashed and it showed a B16 code for a veh anti theft box, they ordered one of those and installed, now it will not program, will not read the vin#. The dealership now thinks we need a PCM ( power train control module) now. They are expensive!!!!!!!!!!! ($1070)
Someone else must have had this problem before, or looked at one, all we did was change batteries, no aftermarket stuff on it.
DO NOT LET THEM CHANGE THE PCM yet.
It sounds like the problem lies in the decoder in the ignition, not the VATS nor the PCM.
As stated before, the decoder acts like a multimeter to decode the resistance in the key used in the ignition. When it is defective, the wrong resistance is given the PCM, thus a tech MAY THINK the PCM is faulty, but the problem isn't very likely there. Think steering column.
There are fifteen different resistance values GM uses in their VATS keying. The PCM has your key value stored in it and replacing the PCM will only serve to remove that value until it reads that of your key, if it can. Me sees a problem transmitting that value you already have to the module, not in the module's interpretation of it. That sounds like it's in the ignition switch.
I do want you to check two fuses to eliminate these outright: in the UH BEC (underhood fuse panel), check fuse #'s 16 and 38, both are 10A. #16 is the leftmost 10A fuse in the second row left of the PARK LP relay. This one supplies power to the PASS-key module.
#38 is the 10A to the left of the IGN 1 relay, under the 15A. This one supplies power to the BCM.
If these fuses are good, the next place to troubleshoot would be the ignition switch itself. A good cleaning of both the keys and the PASS sensor with a Q-Tip and denat'd alcohol could help. DO NOT USE LUBRICANTS on these systems.
Hope you the best,
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