Multiple bad PCMs?

Jeff Owner/Technician Arizona Posted   Latest   Edited  
Unsolved
Parts
Programming
2004 Dodge Intrepid SE 2.7L (R EER) 4-spd (42LE) — 2B3HD46R74H621534
P0352 — Ignition Coil "B" Primary Control Circuit/Open
Misfire

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?

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Helpful
Stephen Technician
Tennessee
Stephen
 

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…

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Alan Owner/Technician
Iowa
Alan
   

Nevermind - delete

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Alan Owner/Technician
Iowa
Alan
 

And you can still install the original PCM with only a knock sensor code? Alan

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Jeff Owner/Technician
Arizona
Jeff
 

Correct.

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Clint Technician
Illinois
Clint
 

I try a used ECM. Junk yard should have a ton of them cheap because those engines are junk.

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Agree
Jeff Owner/Technician
Arizona
Jeff
 

If only. All the junk yard Chrysler stuff dried up in 2020.

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John Owner/Technician
Iowa
John
   

Have you checked on car-part​.​com

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Bentley Manager
California
Bentley
 

Try scoping the amperage on all the coils and see it #2 looks different.

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Jeff Owner/Technician
Arizona
Jeff
 

Did that as well as monitored fly-back. All 6 coils are the same.

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Eric Owner/Technician
Wisconsin
Eric
 

Can you share the waveform capture of the ignition coils with us? Thanks,

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Jeff Owner/Technician
Arizona
Jeff
 

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.

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Joel Mechanic
California
Joel
 

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

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Jeff Owner/Technician
Arizona
Jeff
 

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.

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Joel Mechanic
California
Joel
   

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…

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Jeff Owner/Technician
Arizona
Jeff
 

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.

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Marvin Mechanic
Mississippi
Marvin
 

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…

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Eric Owner/Technician
Michigan
Eric
 

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.

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Funny
Jeff Owner/Technician
Arizona
Jeff
 

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.

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Jesse Engineer
Missouri
Jesse
 

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…

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Maynard Technician
Ontario
Maynard
 

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…

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Jeff Owner/Technician
Arizona
Jeff
 

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…

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Dmitriy Analyst
Ontario
Dmitriy
 

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.

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Helpful
Interesting
Jesse Engineer
Missouri
Jesse
 

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…

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Steve Technician
Pennsylvania
Steve
   

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…

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Jeff Owner/Technician
Arizona
Jeff
 

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.

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Jesse Engineer
Missouri
Jesse
 

Send them to Car-part​.​com Plenty of factory units available ebay. Just make sure and match part numbers.

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