Did the PCM fail?

Joined
Apr 16, 2016
Messages
1,985
Location
Kansas
I was driving my 09 P71 Crown Victoria last night to a call. Got done with the call came back and the CEL came on. Now I have no AC. A ton of CEL codes. Car won't shift out of 1st and has almost no power.

I checked all the fuses and relays. Nothing seems to be wrong there.

Screenshot_20200725-052425.png
Screenshot_20200725-052439.png
 
Without being able to look at it and do some testing I will guess, it sounds to me like it lost B+ momentarily to a whole circuit, check the obvious like battery cables and voltage, the cable that power the engine fuse/relay box, etc.
 
Do not forget grounds . Both to the chassis and engine .

I agree , remove the battery cables , clean them and the battery posts very well . Look for damage at the cable / clamp interface . REplace if corroded / damaged . Treat the post / clamps with your favorite anti-corrosion product .

By now , the " computer should be reset & codes cleared .

Best of luck to you .
 
THe common point for all of those components (trans solenoids, compressor clutch relay, oxygen sensor heaters) is FUse 21 in the battery junction block. Power to fuse 21 comes from the PCM power relay. Check for power to both sides of fuse 21 key on and we can go from there
 
Try swapping the relay with another in the fuse box (make sure they’re identical part numbers). I’ve had a relay go bad before (it was sticking) and this was an easy way to troubleshoot it (the weirdness moved with the relay).
 
Try swapping the relay with another in the fuse box (make sure they’re identical part numbers). I’ve had a relay go bad before (it was sticking) and this was an easy way to troubleshoot it (the weirdness moved with the relay).
Waste of time. Per the wiring diagram the PCM power relay supplies power to the fuel injectors and coils. Car woulndt run at all with a failed power relay
 
Done this before? Was it fixed, or did it fix itself? If the latter then it sounds like it'll be fun chasing wires.
 
I was just informed that this isn't the first time it's done this. I'm guessing a bad ground somewhere.

Those are all ground side switched/controlled components fed by the the same fuse......I'd bet money you have a power feed problem in that circuit.

Timmastertech already pointed that out, Don't know why that was ignored?? If intermittent.....Check for good contact at the fuse, The terminals could be stretched out.
 
Back
Top