[CanBum]

I think I have a bad PCM, need a little help trying to diagnose it. Car is a 2013 GT Base track pack car. I installed a Kenne Bell 3.2L SC and it ran fine for a few weeks. I drove it then parked it in the garage then went to start it the next day and it’s throwing a bunch of codes and not cranking. The anti theft light is on along with service advance track and a TPMS light. Tail lights and head lights are flashing too. It was a hot day in Chicago, I’m thinking the PCM went. Car had zero issues then I go to start it and bam. I pulled the battery out and put a different one in there, same issues.

Codes
U0100
U0121
B1218
U0401
U0121
U0028
U0256

 

[crjackson]

Looks like a damaged wiring harness, or not plugged in tightly.

Just my worthless 2¢

 

[CanBum]

Looks like a damaged wiring harness, or not plugged in tightly.

Just my worthless 2¢

Thanks, I’ll take a look and see if there’s anything obvious that looks off

 

[AndyEckel]

Ouch. That is a nasty combination of codes. Heat could very well be a contributing factor. My quick thoughts:

* +1 for definitely checking the wiring harness, especially at the PCM. Look for obvious signs of heat damage. That is a best case scenario. But check the whole harness with a thorough visual.

* If nothing is obvious from above, Check the electrical resistance between pins 6 & 14 on your OBD-II port. It should read 60 ohms +- 1 ohm. Use T-pins. This is a very basic CanBus check as a first step. If out of range, that is a red flag you have a failed module(s) and/or bad wiring harness issues.

* Don't be surprised if the resistance reading is within range. You can still have a failed PCM. The PCM is the proverbial heart of the circulatory communication system. You could have had a proverbial heart attack (bad PCM) without a liver module failure or blood clots - to use an analogy.
----
My questions & recommendations
1) You stated "I installed a Kenne Belle SC..." Did you actually install it yourself? More importantly, how did you get it tuned?

2) Assuming you had a dyno tune, because it "ran fine for a couple of weeks", I would next simply try to re-flash the tune. You have nothing to lose. Contact your tuner too.

3) If this does not help and you still get the same codes, I would be looking for an absolute expert that can perform CanBus diagnostics with an oscilloscope. This could be as simple as going back to your tuner and asking for such help. Be mindful you could be a "victim" of sheer poor luck with a pooped out PCM and there is no fault with the tune. If you had your car tuned at a reputable shop, they should be able to help. If you got a flash tune and did a DIY, and you still have no luck, I would consider having it trailered to Brenspeed in Pierceton IN. IMHO, that's your best option as a last resort.

HTH & best wishes
Andy

 

[CanBum]

Ouch. That is a nasty combination of codes. Heat could very well be a contributing factor. My quick thoughts:

* +1 for definitely checking the wiring harness, especially at the PCM. Look for obvious signs of heat damage. That is a best case scenario. But check the whole harness with a thorough visual.

* If nothing is obvious from above, Check the electrical resistance between pins 6 & 14 on your OBD-II port. It should read 60 ohms +- 1 ohm. Use T-pins. This is a very basic CanBus check as a first step. If out of range, that is a red flag you have a failed module(s) and/or bad wiring harness issues.

* Don't be surprised if the resistance reading is within range. You can still have a failed PCM. The PCM is the proverbial heart of the circulatory communication system. You could have had a proverbial heart attack (bad PCM) without a liver module failure or blood clots - to use an analogy.
----
My questions & recommendations
1) You stated "I installed a Kenne Belle SC..." Did you actually install it yourself? More importantly, how did you get it tuned?

2) Assuming you had a dyno tune, because it "ran fine for a couple of weeks", I would next simply try to re-flash the tune. You have nothing to lose. Contact your tuner too.

3) If this does not help and you still get the same codes, I would be looking for an absolute expert that can perform CanBus diagnostics with an oscilloscope. This could be as simple as going back to your tuner and asking for such help. Be mindful you could be a "victim" of sheer poor luck with a pooped out PCM and there is no fault with the tune. If you had your car tuned at a reputable shop, they should be able to help. If you got a flash tune and did a DIY, and you still have no luck, I would consider having it trailered to Brenspeed in Pierceton IN. IMHO, that's your best option as a last resort.

HTH & best wishes
Andy

Thanks a lot for the thorough response. Here are answers to the questions you have.
1) I did install it myself. It came with a Kenne Bell proprietary flash tuner supplied by them with the kit. The last step on the install is to flash the pcm with their tune. Kenne Bell had specific questions on the pcm I had when I ordered the kit and needed my pcm code (DHW0) to write a specific tune I’m assuming. It initially flashed just fine and did run just fine for a few weeks, till this happened. No issues at all.

2) I did try and reflash it using the same Kenne Bell supplied dash tuner. It was able to reflash the tune successfully according to the readout on the tuner through the whole process. Nothing changed though after the reflash. Same issue

3) I will try and contact Kenne Bell as well to see if they can help.

I will also give your OBD2 test a try, I have a multimeter and it seems pretty straightforward.

I found a used PCM online with my same part number (dr3a-12a650-aha) and bought it at a fair price. I plan on keeping the car for a very long time so worse case scenario is I have a spare. I am not just going to pop it in though. I’m afraid if there is some sort of a short it might fry the replacement pcm.

Once I try the OBD2 plug test I’ll report back. Appreciate the help, it’s been challenging to try and figure out what this is.

 

[AndyEckel]

CanBum -

You are absolutely on the right track and doing all the right things! You scored good with an exact replacement PCM. Well done!

Yes, you should check all your fuses. I discovered this link below on this forum sometime ago and saved it for my reference. It is a complete wiring diagram for a 2011-2014 S197 Mustang. It has help me on many occasions and I wanted to share it with you in case you don't have it.
Ford Workshop Service & Repair Manuals - fordrepair.info - 2011 Mustang 2011 Mustang 009 - wiring harness overview (iihs.net)

For example, you could use this bit shown below to check all your powers and grounds to the PCM. Somewhat surprisingly, there are more than one! Mind you, this is tedious & delicate & difficult and time-consuming trouble shooting But you can backprobe (again with automotive T-pins) the big connectors at the PCM
These pins should allhave 12V power - note some are constant power and some are KOER

• Pin 62 white-red wire
• Pin 68 green-blue wire
• Pin 67 green-blue wire also
• Pin 42 yellow wire

Likewise, pins 69, 70 & 50 - each Black-Blue - go to ground and are easy to test once you can get your hands on them!

Hint: A best practice of mine was to print these in color at my work office after / before regular hours on 11" x 17" ledger size paper. We were allowed "incidental use" of all the IT equipment for stuff like this. Makes the task a lot easier and it good to have to mark-up the ones you've already tested.

This would be my next step. If everything checks out, it is another nail in the proverbial coffin before you decide to put your PCM in the graveyard. You can save yourself several hundred bucks in labor and a tow by doing this too!

You could also use the CanBus diagrams in Section 14 to your advantage. This is where things get real tricky, real fast and now you're searching and finding all those modules that your PCM can't "talk" to on the network. I have seen some instances where one bad module, e.g. the TCM, because of the way everything is connected together, can seemingly corrupt a lot of other things. This is kind of like parasitic draw testing. You can just start unplugging modules - should you wish - one by one and see if one unplugged modules clears all the codes (except for itself).

This thread shows the pin locations at the PCM!
PCM Technical help needed - Please Read | Ford Mustang Forum (allfordmustangs.com)

HTH and keep up the good work.
Andy

PS: Please post back when you know more. It helps everyone learn.

 

[Cobrajet67]

Thanks a lot for the thorough response. Here are answers to the questions you have.
1) I did install it myself. It came with a Kenne Bell proprietary flash tuner supplied by them with the kit. The last step on the install is to flash the pcm with their tune. Kenne Bell had specific questions on the pcm I had when I ordered the kit and needed my pcm code (DHW0) to write a specific tune I’m assuming. It initially flashed just fine and did run just fine for a few weeks, till this happened. No issues at all.

2) I did try and reflash it using the same Kenne Bell supplied dash tuner. It was able to reflash the tune successfully according to the readout on the tuner through the whole process. Nothing changed though after the reflash. Same issue

3) I will try and contact Kenne Bell as well to see if they can help.

I will also give your OBD2 test a try, I have a multimeter and it seems pretty straightforward.

I found a used PCM online with my same part number (dr3a-12a650-aha) and bought it at a fair price. I plan on keeping the car for a very long time so worse case scenario is I have a spare. I am not just going to pop it in though. I’m afraid if there is some sort of a short it might fry the replacement pcm.

Once I try the OBD2 plug test I’ll report back. Appreciate the help, it’s been challenging to try and figure out what this is.

The PCM would have to be flashed with your original Ford program and then reflashed with the custom tune. As I understand it, without it being initialized with the instrument cluster it would basically be a brick and not start the car.

CanBum -

You are absolutely on the right track and doing all the right things! You scored good with an exact replacement PCM. Well done!

Yes, you should check all your fuses. I discovered this link below on this forum sometime ago and saved it for my reference. It is a complete wiring diagram for a 2011-2014 S197 Mustang. It has help me on many occasions and I wanted to share it with you in case you don't have it.
Ford Workshop Service & Repair Manuals - fordrepair.info - 2011 Mustang 2011 Mustang 009 - wiring harness overview (iihs.net)

For example, you could use this bit shown below to check all your powers and grounds to the PCM. Somewhat surprisingly, there are more than one! Mind you, this is tedious & delicate & difficult and time-consuming trouble shooting But you can backprobe (again with automotive T-pins) the big connectors at the PCM
These pins should allhave 12V power - note some are constant power and some are KOER

• Pin 62 white-red wire
• Pin 68 green-blue wire
• Pin 67 green-blue wire also
• Pin 42 yellow wire

Likewise, pins 69, 70 & 50 - each Black-Blue - go to ground and are easy to test once you can get your hands on them!

Hint: A best practice of mine was to print these in color at my work office after / before regular hours on 11" x 17" ledger size paper. We were allowed "incidental use" of all the IT equipment for stuff like this. Makes the task a lot easier and it good to have to mark-up the ones you've already tested.


View attachment 794169


This would be my next step. If everything checks out, it is another nail in the proverbial coffin before you decide to put your PCM in the graveyard. You can save yourself several hundred bucks in labor and a tow by doing this too!

You could also use the CanBus diagrams in Section 14 to your advantage. This is where things get real tricky, real fast and now you're searching and finding all those modules that your PCM can't "talk" to on the network. I have seen some instances where one bad module, e.g. the TCM, because of the way everything is connected together, can seemingly corrupt a lot of other things. This is kind of like parasitic draw testing. You can just start unplugging modules - should you wish - one by one and see if one unplugged modules clears all the codes (except for itself).

This thread shows the pin locations at the PCM!
PCM Technical help needed - Please Read | Ford Mustang Forum (allfordmustangs.com)

HTH and keep up the good work.
Andy

PS: Please post back when you know more. It helps everyone learn.

All good advice but there is no TCM in the Mustang at least up to the 2014 as the transmission control is integrated with the PCM and always had been. I've also never heard of any TCM being in the 10R80 auto equipped models from 2018-23. It's possible that the last GT500s with the DCT trans may have had a separate TCM though, idk. Other Ford models sometimes had a separate TCM like in the notorious 2012-18 Focus with the DCT trans.

I also recommend checking basic system power and ground connections especially when hit with a bunch of unrelated, unusual, and unlikely codes. You have communication codes with the PCM, ABS, FCIM, and key transponder(PATS). A poor ground connection at the engine block or various body points can cause strange electrical gremlins as can a bad power connection somewhere. The PCM relay is something to test and maybe swap if there's another of the same part # in the fuse box. Also, look at any of your relevant fuses to make sure that none have blown. There are several for the PCM for instance.

 

[CanBum]

Thanks for the advice. I’m hoping to get some time to start looking at it this week. Will report back with any results.

 

[2012GTRed]

I also recommend checking basic system power and ground connections especially when hit with a bunch of unrelated, unusual, and unlikely codes.

Yes the fact that it's not cranking makes me think of a rusty ground I saw when I was under my car yesterday. It's on the side of the block (passenger side), kind of near the front. The ground cable came out of the harness that had a lot of things on it. I believe the starter, O2 sensors, alternator, etc...and that harness went to the PCM and the battery I believe. I couldn't reach it so I just sprayed some lube on it, but I may add another ground strap or two from the battery to the engine to compensate for that one. A quick test would be for the OP to connect a jumper cable from the negative post on the battery to somewhere on the engine and maybe another one from the negative post to the PCM bracket.

 

[CanBum]

Thought I’d send an update on this. Finally got it fixed, it was a (Moderated) to figure out. Main wire loom that runs by the abs module and pump rubbed through the loom and was grounding two wires as shown. I cut out the bad parts of wire then soldered a patch piece in and used heat shrink tubing to seal the solder joints. Rewrapped the wire bundle then reinstalled the loom and trimmed that sharp piece of metal back. Once I cleared all DTCs in Forscan and did a Pats relearn everything went back to normal. This was not fun at all. Thanks to everyone that helped. I appreciate it. I wouldn’t wish wiring problems on my worst enemy, they are maddening.

 

[AndyEckel]

Appreciate you closing the loop! It really helps others learn.