THE 1

all the basics you mentioned are ok. I need to know how to diagnose a bad PCM ? Car barely runs,slowly has gotten worse and no codes? How is this possible unless computer is going bad ? If the engine was shot or the can was going, it should smoke or throw some kind of code or something, any ideas ? Thanks

Urambo Tauro

The book does mention a Rotunda (dealership) EEC-IV Monitor tool that lets you check signals going in and out of the PCM. Since your car is OBDII, I imagine you'd need an OBDII scan tool (a real scanner, not just a code reader) in order to do that. I don't think there's any way to quickly diagnose a bad PCM, unless you're "lucky" enough to not be able to connect to it at all. (Maybe someone else can comment with another quick check that I'm overlooking.)

While PCMs have been know to fail from time to time, bad sensors or wiring faults are far more likely, and it would be in your best interest to rule out other stuff first. That's how the flowcharts are designed, to make sure that the PCM is receiving the correct signals before we condemn it for sending the wrong ones. You do NOT want to waste money on replacing a PCM if all you have is a damaged wire somewhere.

I would recommend selecting a specific symptom, (like one of these) first: