New Engine Install - Rough start then Stalls

[alphawolff]

I just completed the pin drag test of the Power Distribution Center connectors. I have not done the PCM harness meter test yet. Moving slow here. Wrenched my back last weekend.

To be clear, which is the C1 connector?

Forward connector.

Rear connector.

The top picture is the C1 connector. The forward one.

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[roaniecowpony]

Ok, performed the tests. Readings are hand writen on the picture below. Looks like everything is in spec except the Ground on pin #53.

Edit: missed pin 72... Good ground there too.

Edit 2: miscounted the 52-53 pins. Found my error after pulling the backshell and seeing the blk/grn wire locations. New pix below.

 

[Bill_BCNtoNY]

Ok, performed the tests. Readings are hand writen on the picture below. Looks like everything is in spec except the Ground on pin #53.


View attachment 891935

I really hope that ground is the culprit and that fixing it isn’t too much of a wiring nightmare!

this thread feels like when I sit back and root for the good guys from the couch as if I was watching a superhero movie

 

[roaniecowpony]

I really hope that ground is the culprit and that fixing it isn’t too much of a wiring nightmare!

this thread feels like when I sit back and root for the good guys from the couch as if I was watching a superhero movie

After finding my counting error above (edited), I feel like a superzero.

 

[roaniecowpony]

Waiting to hear back from @alphawolff. But it is looking more like the PCM is the problem.

 

[alphawolff]

Looking at your readings and seeing we've got both power circuits, all 3 grounds, and both can circuits working properly it is indeed a failed PCM. Reinstall your old one to double check with another scan tool to confirm the PCM isn't communicating just to make sure it's not the scan tool itself that isn't communicating. If it still isn't go ahead and replace it. I don't know if the 18s all had a security gateway, but if it does you might need to disconnect it and install a bypass connector for a 3rd part scan tool to properly talk to the vehicle.

Nice job. You'll have to have a dealer program the new PCM, though. Hopefully there's nothing else going on that caused it in the first place. I have seen PCMs just outright fail before, it's just rare.

 

[roaniecowpony]

Looking at your readings and seeing we've got both power circuits, all 3 grounds, and both can circuits working properly it is indeed a failed PCM. Reinstall your old one to double check with another scan tool to confirm the PCM isn't communicating just to make sure it's not the scan tool itself that isn't communicating. If it still isn't go ahead and replace it. I don't know if the 18s all had a security gateway, but if it does you might need to disconnect it and install a bypass connector for a 3rd part scan tool to properly talk to the vehicle.

Nice job. You'll have to have a dealer program the new PCM, though. Hopefully there's nothing else going on that caused it in the first place. I have seen PCMs just outright fail before, it's just rare.

Thanks very much for all the guidance @alphawolff. I could not have done all this without your help.

The PCM is currently across the country in Florida at a PCM repair shop. He's going to test it first, then call with the results. I have a friend that has a good PCM he offered to give me. The repair shop will program a PCM for $100.

 

[roaniecowpony]

Looking at your readings and seeing we've got both power circuits, all 3 grounds, and both can circuits working properly it is indeed a failed PCM. Reinstall your old one to double check with another scan tool to confirm the PCM isn't communicating just to make sure it's not the scan tool itself that isn't communicating. If it still isn't go ahead and replace it. I don't know if the 18s all had a security gateway, but if it does you might need to disconnect it and install a bypass connector for a 3rd part scan tool to properly talk to the vehicle.

Nice job. You'll have to have a dealer program the new PCM, though. Hopefully there's nothing else going on that caused it in the first place. I have seen PCMs just outright fail before, it's just rare.

To your recommendation to try another scan tool, i checked it with two different scan tools, with the security gateway bypassed.

 

[DaltonGang]

I need a drink, after reading this thread. This is exactly why I don't do electrical.

 

[roaniecowpony]

I need a drink, after reading this thread. This is exactly why I don't do electrical.

I just feel like I have to learn some electrical/electronics skills. These damn things are full of that stuff. Being good at mechanicals will not carry the day, anymore.

 

[Terrymo]

I just feel like I have to learn some electrical/electronics skills. These damn things are full of that stuff. Being good at mechanicals will not carry the day, anymore.

Seems like you have the patience, perseverance, and the logical mind to pull this off.

 

[roaniecowpony]

Well, not great news. The PCM shop said my PCM was communicating. They sent it back. No charge.

So, back to square one.

I decided to check the PCM connector socket tension. I made a pin gauge from a large .025" thick X-acto blade. All the sockets were good.

 

[alphawolff]

Well, not great news. The PCM shop said my PCM was communicating. They sent it back. No charge.

So, back to square one.

I decided to check the PCM connector socket tension. I made a pin gauge from a large .025" thick X-acto blade. All the sockets were good.

Plug the PCM back in and check the scan-tool once again. If you're unable to communicate with the PCM and the test we did before is still identical then the PCM is indeed faulty. I would not trust a third party "testing" the module as a rule of thumb, sorry. This wiring test combined with the loss of communication from a scan tool is what Stellantis themselves tells us to do to diagnose a communication failure with a module. It has always proven accurate in my experience.

Remember this was all based off the scan-tool failing to communicate with the PCM. You said you tried multiple scan tools, so I'm assuming they're working correctly. Some third party scan tools don't work properly with our vehicles.

 

[roaniecowpony]

Plug the PCM back in and check the scan-tool once again. If you're unable to communicate with the PCM and the test we did before is still identical then the PCM is indeed faulty. I would not trust a third party "testing" the module as a rule of thumb, sorry. This wiring test combined with the loss of communication from a scan tool is what Stellantis themselves tells us to do to diagnose a communication failure with a module. It has always proven accurate in my experience.

Remember this was all based off the scan-tool failing to communicate with the PCM. You said you tried multiple scan tools, so I'm assuming they're working correctly. Some third party scan tools don't work properly with our vehicles.

Thanks again for your experience. Yes, one of the scan tools was used by me for over a year. It's bluetooth. But it has history of working. The other was a borrowed Autel unit, plugged in directly to a security gateway bypass harness.

I took the time to make a gauge to check the PCM connector sockets. All good.

I hope you're right about the PCM being bad. I'll get another and try it. Can I try it out without VIN programming? Or is the VIN programming necessary for starting it?

 

[2nd 392]

I hope you're right about the PCM being bad. I'll get another and try it. Can I try it out without VIN programming? Or is the VIN programming necessary for starting it?

All Mopar Parts was $245 under MSRP on mine + a 50% shipping discount ($15) from Benny.
Good luck, you are due some.

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