Repeated PCM Failure

The voltage spike on the ground is interesting. Where do you have your ground lead hooked? I think a trace of the voltage supply to the ignition coils would be in order. Over the years, the only thing I have ever seen that would cause voltage spikes like is some very high resistance in the ignition secondary. From memory, there should be a capacitor on each cylinder bank that is hooked to the…

That ground is at the battery , but it's the same every where I hook it to , capacitors came to mind as well but I didnt see any on the wiring diagram (doesnt mean there not there ) you mentioned high resistance in the secondary which makes me think I read somewhere about Chrysler spark plugs causing weird electrical issues. I have channel D set to AC and on the Alternator post and you can see…

Although ignition spikes are always visible on the ground, (and a good trick to ID a misfire), spiking to 13 volts is crazy bad for an ECM I think. Around that time-frame there are numerous cases of mystery stalls with no DTC set, all from ignition spikes. IIRC there was even a TSB basically stating to make darn sure all the spark plugs are 100% correct OE for the application. Pretty sure they…

Had a Durango that had trans codes and blown fuse for the transmission. After replacing the fuse and trying to trace the short, Lost communication with the ECM/TCM. Turned out the wiring harness down by the trans had the insulation on the wires disintegrate inside the tape. Wires shorted together and fried the ECM. Fixed the harness and replaced the ECM and all was good. Good luck!

I see igniton spikes on sensor waveforms all the time with the scope. Ignition creates alot of electrical noise that can be transferred to other circuits with induction. Could be just the way your leads are run in the engine bay. I use them for diagnostics sometimes to see if there is spark while using the channel for other signals.

I have seen the same problem, but the short would take out a pcm at the first key cycle. His problem is way more intermittent.. I have seen a lot of Chrysler ecm failures that were due to cracks in the circuit board. Flexing the connector can sometimes make the problem appear and disappear.

This vehicle had been having transmission issues and blew the fuse a few times before coming into the shop. I hooked up my short detection tool that pulses to find the short. Even though the computer was not turned on by the time I found the short the computer was fried and the truck would not start and no communication with the ECM. With all the trans codes I would take a good look at the…