Multiple bad PCMs?
I got called in for a knock sensor diag on this car several weeks ago. I called the PCM because it was reporting a phantom voltage regardless of what was actually on the wire.
The “new” PCM shows up 3 days ago (probably a Cardone reman from NAPA). I drop it in, write the VIN and start it up.
P0352 pops after 10 sec or so and then a misfire on #2.
I swapped the coil and plug with #1, but the miss and the drop stay on cylinder #2.
I ohm-out the wire, as well as watch the signal on the coil. It is clearly firing that coil, but pulling the injector after 10 seconds. Swapping back in the original PCM corrects this issue.
So, I tell them to get another PCM.
Next PCM shows up in the story is exactly the same as above.
Do it a third time today. Same story.
What am I missing?
It appears that the ECM can’t see that the #2 is firing. How is that function monitored? Flyback voltage? I wonder are the coils OE? Plugs? Software version in the new ECMs different than original? Maybe put a ferrite bead on the coil trigger wire or a .02-.047ufd capacitor to ground on the coil lead? More invasive would be frog 2’s coil lead with another coil(also frog the wires are the ECM) to…
And you can still install the original PCM with only a knock sensor code? Alan
I try a used ECM. Junk yard should have a ton of them cheap because those engines are junk.
If only. All the junk yard Chrysler stuff dried up in 2020.
Try scoping the amperage on all the coils and see it #2 looks different.
Did that as well as monitored fly-back. All 6 coils are the same.
Can you share the waveform capture of the ignition coils with us? Thanks,
No - I didn't do any captures. Since they were all the same, there was really no point. This isn't about a failed output since we have a known-good PCM that matches the failed units. Just looking for similar experiences with multiple failed #2 coil drivers.
Do all the part numbers on the replacement pcm match up? If not the pcm is probably incorrect. I would send original to a rebuild and have that one fixed
Yes. Both did. I flashed both to verify the calibration as well. However, an incorrect calibration is not going to cause a single coil fault.
No an incorrect calibration won't but a bad driver on the ground side internal to the pcm will. Chrysler pcms can sometimes be very finicky when being replaced though. That's why I usually will have the original pcm sent out for rebuilding. Also on a circuit you always want to do a voltage drop and not ohm out a wire. Resistance is better for determining bad solenoids. Voltage drop is best for…
All fine and well, but isn't useful. “Rebuilding” the original PCM isn't going to happen. Current drop was, as indicated, tested across all 4 PCMs, as well as actual fly-back and trigger voltages. Ohming the wire is needed to prove continuity and disproving shorts across commons.
Those ghost voltages will make you mis diagnose stuff….induced from another wire,,,,,,and wrong wiring diagrams will also.I had one one a 6.4 diesel where it had us checking voltage on a wire from ecu and it was no way it could have voltage with out a relay closed and relay couldnt close because we had harness off..jumped relay with paper clip and had voltage it asked for…
What's more stunning is an 18 year old Chrysler with the ‘bullet proof' 2.7 that is still running. Up here, it is fine if it even starts.
Indeed. Here in AZ there are all kinds of things still on the road that probably shouldn't be. Honestly, it's a type of job security. Long after the market has moved to non-repairable automobiles, we'll still have stuff to do here in Arizona.
Had a similar issue on an 02 Intrepid but with the 3.5. Nice car, would crank, no start. No power to coils or fuel pump which are on the same fuse. Bad design. Diagnosed the heck out of it. Indicated bad PCM. Now, there are 2 PCMS for these. Same part #. Depending if the car has a security key or not. That part has to match. On newer Chargers with same engine setups, 2.7 & 3.5, the computers…
I dont know how much work you are interested in doing to try making the replacement Pcms work. However, when you read the diagnostic description of the set conditions it has a few interesting things. It suggests if PEAK current is not achieved…code sets within 6 seconds when car is running. So if you were to take a diode and connect it on the negative side of #2 coil and choose some resister…
I'm not gonna muck about with it too much because: 1) I'm just the mobile guy 2) This bit of ancient history really shouldn't still be on the road, so I'm not too keen on being responsible for its continuation thereof That said, I'm more curious as to why this is only an issue with the replacement PCMs, not the original (which was actually replaced by a dealer at some point since its…
There is an ancient article about ancient Dodges that says CKP and CMP sensors could cause spurious codes: underhoodservice.com/tech-tip-dodge… Not sure if it applies to this case, but food for thought.
I've heard a lot of issues with aftermarket/rebuilt PCMs. Electronics in the boards can be finicky. Since they all came from the same supplier, I'd say they are building them differently or changing a component that is causing the issue. I'd find a used computer at a salvage yard that had a matching VIN. At least its factory most likely. Dodge ends up issuing updates to PCMs if issues arise…
Not a Chrysler, but on the topic of reman modules being faulty: A couple of years ago i had a Cadillac with a bad ECM; it was not waking up and coming online even though wake voltage from the PMM was present at the connector. I diagnosed it as being definitely internal to the ECM, and ordered a reman Delco one from our local Delco warehouse. Installed it, went to program and couldn't because…
Thanks so much for that. Exceptionally resonant with me. Unfortunately, Cardone is all this customer seems to have access to (NAPA and O's) and I don't really have much say in it. Trip number three is coming up on Friday.