2018 Mustang GT completely bricked

[jack28baker]

Making this post for a friend, but he has a 2018 Manual Mustang GT, recently he had it tuned, and about 5 mins after it was tuned he went over a divot in the road and car sputtered out and stalled. Since then, every dash light has come on, had no power to obd2, car didn’t even know how many miles it had. Since then he had a guy come over and used a software to try to unlock some things. He put a new pcm in the car and it communicated with obd2 and now shows miles but the issue still persists, and obd2 can only be accessed by the ford software the guy had, not a regular scanner. We checked all fuses and none were blown. Headlights still turn on so we assume bcm is still good. As a loss as to what to do now, any recommendations?

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[FiveOh500]

Sounds like the tune might have corrupted something in the PCM when it hit that bump - I'd try having Ford reflash it back to stock tune first before throwing more parts at it.

 

[Swtbabybilly]

Agree with the post above id be getting it flashed back to stock asap but you could also check all the grounds make sure none of them broke off when he hit the divot,

By the way who tuned it? You could reach out to them, best of luck

 

[G.T.]

On related vids I watched online, a no-com like that could be caused by problems in wiring junctions or components that fail in series.

Sounds like a communication/canbus/electrical problem that may not necesarily be the tune?

I think you need someone with a wiring diagram and knows how to use it.

EDIT: either way, bringing things back to stock will help narrow it down and is recommended.

I've seen guys who diagnose stuff like that for a living stipulate the car must be flashed to stock before they work on it.

 

[Airborne5.0]

Who "tuned" it?

 

[Cobra Jet]

Yea, I mean driving and hitting a “divot”, pothole, road imperfections - the tune has no bearing at all on it “bricking” itself or making the car go limp.

There’s an electrical issue somewhere and you need to start doing tracers to find out if it’s a ground (as mentioned above), or if it is a connector or wiring harness that has become loose, if perhaps a wire harness has been damaged and is shorting out, or something along the PCM tract has become damaged and is not allowing proper communication.

There’s no way in hell a “tune” can brick and S550 by driving over anything in the road or by being bumped/jarred…. The tune is SOFTWARE…. The issue your friend is having is most likely HARDWARE related (wiring, connectors, modules, PCM damaged from shorting, grounds, etc).

Was your friend able to pull any codes at all and if so, list them all.

Check the harnesses under the car and make sure none of those harnssss have come in contact with the hot exhaust and got damaged, chafed, or torn when he hit so called divot. Also go to rear of car and if it has active exhaust, make sure the short harnesses at the mufflers didn’t get damaged or shifted against something breaking the wires under the conduit…. This is a known issue for active exhaust S550’s but normally NOT one that would put the car into limp mode or brick it.

You need a S550 wiring diagram and some good old fashioned diagnostic work to trace wires to the PCM and possibly determine why the car has shorted.

—-

One thing that comes to mind is IF the “hit” was hard enough, and IF it somehow triggered part of the SRS system but did NOT deploy an airbag, the SRS system fault codes are totally separate from the normal PCM fault codes. These codes cannot be retrieved using a normal ODB scanner. IF the SRS system RCM was somehow triggered (even if it didn’t deploy anything) it will throw the car into limp mode if the system thinks there was an accident. It’s not far fetched, it depends on how hard this friend hit whatever he hit. I don’t believe it is the issue, BUT that is the only other system I know of that will prevent a S550 from starting and communicating IF it has a SRS fault from an RCM event.

Here’s one of my SRS threads, scroll down to bottom in it and read about the RCM and info on how to start after a trigger event:
https://www.mustang6g.com/forums/threads/airbag-light-b1404.222645/#post-4390232

 

[Cobra Jet]

Oh and one more link for you, this thread contains lots of links for no-start condition:

https://www.mustang6g.com/forums/threads/sos-car-won’t-start-solved.174650/#post-3536784

In the above link, read the one about the GT350 owner and the 125 Amp fuse that is under the hood near the battery distribution block - this caused an interim bricking of the car and no-start condition.

 

[Skye]

The short version

- Loose connectors involving the GateWay Module

- Loose connectors involving the Powertrain Control Module

- Tuning while driving, committing in the middle of something, corruption in the PCM

- Donor PCM, a piece that's seen a lot of miles, hands and re-flashes

The long version

I does read like it's more electrical than coding.

The chips in the PCM are firmware. The pieces are designed to spend their lives taking strikes from potholes. You'd have to break a chipset or solder board to kill the PCM. It's possible, but it'd be really coincidental in this example.

If he was tuning while driving, hit the pothole and committed in the middle of something, that could have been a big negative. IDK, you'd need to confirm that with your friend. If the driver was simply field testing and not tuning, I'd set the corrupted software concern aside for now.

Before the pothole, the car was at least running. There are a lot of finely-pinned, multi-pin connectors involved, with little slack and tight clearances. I'd focus on those.

Don't assume anything. There've been multiple people with their hands on the car. Run through every junction and connection to ensure they're secure. If aftermarket pieces were installed as part of the project (like a fuel pump, injectors, etc.), you'll need to review those.

When the second PCM was introduced, that changed things. The PCMs are coded with the car's VIN and must match the drivetrain. That the second person could read it with their software makes sense. That it didn't work in the car also makes sense. It depends on how the second PCM was coded.

I'd go back to whatever PCM was in the car before. Check, confirm all connections and attempt to access it. If you can, temporarily flash it back to the stock build and see what happens. If you can't, it'll need to be returned to whoever tuned it. Have them access it and attempt to flash it back.

Edit:

It's unclear to me the lineage of the PCM that was in the car at the time of the event. If it was the original, OEM PCM that came with the car or a donor from a tuner that had been re-coded. Some do buy donor PCMs and have them flashed. I feel it's best to unwind things as much as possible, using the original PCM.

Edit (Again):

There's another piece involved, one which has seen more activity than the physical PCM under the hood: the GateWay Module (GWM). The GWM is the DataLink Connector (DLC)/On-Board Diagnostics (OBD) port that people are plugging into. It acts as a physical place to hock up. It also acts as a switch/hub for all the network segments.

The front of the GWM is what you attach to. The back of the GWM is the central hub for the network segments.

I don't think the GWM was broken during the event. But with people physically accessing it several times, any of the connections involving the GWM might have loosened up. Gently, check this area to ensure everything is connected well and in-place. A GWM with poor connections could produce any of the effects being witnessed. A poorly-fitting or bad OBD cable being used to hock up could also produce problems.

 

[ORRadtech]

Other than the tune what work has been done recently? Modifications, etc? I'm having trouble believing that the tune alone would be the cause of this although it could make troubleshooting difficult if not impossible.
What aren't you telling us?

 

[Unas2k5]

Check the fuel tank harness check the harnesses at the bottom of the under hood junction box. You swapped out the PCM? That’s probably the last thing you should've done. Who tuned the car ? Check the main body harness/BCM passenger side inside vehicle

 

[jack28baker]

Making this post for a friend, but he has a 2018 Manual Mustang GT, recently he had it tuned, and about 5 mins after it was tuned he went over a divot in the road and car sputtered out and stalled. Since then, every dash light has come on, had no power to obd2, car didn’t even know how many miles it had. Since then he had a guy come over and used a software to try to unlock some things. He put a new pcm in the car and it communicated with obd2 and now shows miles but the issue still persists, and obd2 can only be accessed by the ford software the guy had, not a regular scanner. We checked all fuses and none were blown. Headlights still turn on so we assume bcm is still good. As a loss as to what to do now, any recommendations?

*EDIT* The car is almost stock, all it had was a tune and long tubes. Ill tell him to try and put his original pcm back in and flash it back to stock but i’m not sure if the scanner will work with obd2 on the original pcm either.

 

[junits15]

Yea, I mean driving and hitting a “divot”, pothole, road imperfections - the tune has no bearing at all on it “bricking” itself or making the car go limp.

There’s an electrical issue somewhere and you need to start doing tracers to find out if it’s a ground (as mentioned above), or if it is a connector or wiring harness that has become loose, if perhaps a wire harness has been damaged and is shorting out, or something along the PCM tract has become damaged and is not allowing proper communication.

There’s no way in hell a “tune” can brick and S550 by driving over anything in the road or by being bumped/jarred…. The tune is SOFTWARE…. The issue your friend is having is most likely HARDWARE related (wiring, connectors, modules, PCM damaged from shorting, grounds, etc).

Was your friend able to pull any codes at all and if so, list them all.

Check the harnesses under the car and make sure none of those harnssss have come in contact with the hot exhaust and got damaged, chafed, or torn when he hit so called divot. Also go to rear of car and if it has active exhaust, make sure the short harnesses at the mufflers didn’t get damaged or shifted against something breaking the wires under the conduit…. This is a known issue for active exhaust S550’s but normally NOT one that would put the car into limp mode or brick it.

You need a S550 wiring diagram and some good old fashioned diagnostic work to trace wires to the PCM and possibly determine why the car has shorted.

—-

One thing that comes to mind is IF the “hit” was hard enough, and IF it somehow triggered part of the SRS system but did NOT deploy an airbag, the SRS system fault codes are totally separate from the normal PCM fault codes. These codes cannot be retrieved using a normal ODB scanner. IF the SRS system RCM was somehow triggered (even if it didn’t deploy anything) it will throw the car into limp mode if the system thinks there was an accident. It’s not far fetched, it depends on how hard this friend hit whatever he hit. I don’t believe it is the issue, BUT that is the only other system I know of that will prevent a S550 from starting and communicating IF it has a SRS fault from an RCM event.

Here’s one of my SRS threads, scroll down to bottom in it and read about the RCM and info on how to start after a trigger event:
https://www.mustang6g.com/forums/threads/airbag-light-b1404.222645/#post-4390232

Yes, agree with this reply, this is absolutely not a tune issue, OP lost some kind of electrical connection when he hit that bump.

Probably made the debug much harder by putting in that new PCM

 

[junits15]

*EDIT* The car is almost stock, all it had was a tune and long tubes. Ill tell him to try and put his original pcm back in and flash it back to stock but i’m not sure if the scanner will work with obd2 on the original pcm either.

Its not the tune. I wouldn't try to flash back to stock, you could make your life even harder if that doesn't work right because of the car's current state. Your buddy has an electrical failure. Putting the PCM back in is a good starting point, then he needs to debug the wiring.

If this car loses connection to critical modules it will freak out like you're seeing.

 

[jack28baker]

Its not the tune. I wouldn't try to flash back to stock, you could make your life even harder if that doesn't work right because of the car's current state. Your buddy has an electrical failure. Putting the PCM back in is a good starting point, then he needs to debug the wiring.

If this car loses connection to critical modules it will freak out like you're seeing.

Yeah, I’m trying to help him as much as I can but its not the easiest trying to worm with him over the phone and only being able to help him work on it one day of the week but I’m thinking somehow a bad ground or maybe a harness got rubbed through somewhere, we just don’t know where to start checking, at the end of the day we will probably have to just go through the entire car with a multimeter.

 

[jack28baker]

UPDATE - some mexican guy just came and fixed it in an hour. We don’t know how because he doesn’t speak english

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