The PCM in my '98 Expy (Limited, V8, AWD, if this makes any difference) has developed an intermittent short to ground on the IAT input. No, it's not the sensor, the connector or the wire harness - it's really inside the box. A brief occasional intake air temperature reading of 700 degrees (or some such) probably won't hurt much anything, but every couple weeks the CEL turns on. Typically it will turn itself off a week later, but I am the type who hates to drive with the CEL on. After all, who knows - perhaps this time it's something serious that needs immediate attention? So I got tired of the scanning/erasing routine and decided to fix the PCM. With nothing visibly wrong inside and no schematics or other documentation, all I can do is replace it. And herein lies the problem: the vehicle is equipped with PATS! If I understand correctly, both the PCM and the PATS module store the key codes and other related info (how many keys have ever been programmed etc). And if this information does not agree between the PCM and the PATS module, the old faithful won't even dream of starting again. I read through the wisdom in the FSM (second volume), and it just refers me to yet another publication called the "PATS repair manual" when it comes to these details. So what the heck can I do? Forget about my DIY convictions and bring the vehicle to the dealer? Diagnostic charge, a new PCM at the dealer's price, possibly also a new PATS module for a good measure, labor (at $120/hr around these parts), key reprogramming fee, shop supplies, disposal fee, a donation to the local boys and girls club, the irresistible Hershey bar while I wait... I can already see the $1000 flying out of my bank account -- all because of a cracked 0.2 cent capacitor or a solder splash on the PCM circuit board. Perhaps it's the cost of peace of mind that PATS affords, but even if by some miracle I get away with half of my guesstimate, it still looks -- how should I phrase it -- a bit out of proportion?
I tried talking to one of the places which prides itself on "remanufacturing" any ECM/PCM under the sun. They will sell me one for a reasonable price, but that's all they could say. If they repair mine, will they guarantee that the stored PATS code does not get wiped out? Don't know! Will I need to tow the vehicle to the dealer if I buy a refurbished one and install it? Ask the dealer! Like that service writer is going to tell me anything else except to bring the vehicle to them for diagnosis...
Anyone in the know with advice? Jim? Tom? My gratitude for your wisdom is guaranteed!