: Pcm Question



93sevillests
07-21-09, 12:03 PM
I have a 1993 cadillac sts with the 4.6 and I am wondering if there is a sure way to find out if the pcm needs to be replaced right now
I dont have any codes showing up on the dash
however when I got the car I had a few i took it to the mech and he fixed them
and he told me I would need to get a new fuel rail, injectors,pcm
i am already out a grip load of cash for the rail and the injectors plus the other ends in outs that the mech fixed


any advice would be helpful
Thanks for your help

Submariner409
07-21-09, 05:38 PM
If you feel that the engine is just not running correctly, there's a better chance that the ICM (Ignition Control Module) under the coils, not the PCM (Powertrain Control Module) is the culprit. You need to run ACDelco Platinum plugs, #41-950, and ACDelco wires. Clean the coil connectors for both plug wires and primary 12V and signal wiring. Check the wiring against the diagrams. It makes a big difference. Google "waste spark ignition" for insight. You may have one or more weak coils - there are 4.

N0DIH
07-29-09, 08:29 PM
The L67 3800 (supercharged NOT the non SC!) coils are a hotter coil. You can get take offs from Sinister Drag Designs in Chicago (http://www.sinisterdd.com/) or Morad Auto (http://www.moradpartscompany.com/) who specializes in 3800's.

Get GM coils not aftermarket. Used are fine, ohm them out to be sure they are good.


If you feel that the engine is just not running correctly, there's a better chance that the ICM (Ignition Control Module) under the coils, not the PCM (Powertrain Control Module) is the culprit. You need to run ACDelco Platinum plugs, #41-950, and ACDelco wires. Clean the coil connectors for both plug wires and primary 12V and signal wiring. Check the wiring against the diagrams. It makes a big difference. Google "waste spark ignition" for insight. You may have one or more weak coils - there are 4.

ewill3rd
07-29-09, 09:43 PM
Why do you think there is a problem with the computer?
I see some information but what is the problem you are after?

N0DIH
07-29-09, 10:00 PM
What he said.... Sorry wasn't paying close attention!

But I have said it a lot before, don't throw parts at it, that only serves to make one broke or just plain frustated. Troubleshooting it takes time and learning or finding someone who does know.

Why would he say rails, injectors and PCM, are they all bad? Which ONE is bad? How did he determine it? It urks me when mechs sell people on the 3-4 things their car had bad on it when only one is. Maybe they need it, but the customer needs to know that too.

If "injectors" are bad, which one, not all surely are bad. If one is bad, then it will miss. And pulling injectors wires one at a time will show the cyl that is not firing, not necessarily if the injector or the coil is bad.

If a COIL is bad you will find 2 cyls bad, if an injector, one.

So pull injectors wires off one at a time with the engine running and note rpm drop. when you get to a cyl or 2 with no drop, paydirt.

Disconnect the IAC so the PCM won't compensate for the idle drop.

Reconnect all when done.

I ohm out coils, primary and secondary and have never had an issue with not finding a good/bad one.



Why do you think there is a problem with the computer?
I see some information but what is the problem you are after?