Permanent DTC codes

[JohnK]

I'm posting this as a cautionary tale for others.

When I first started my gen2 coyote, the MIL (malfunction indicator light) wasn't working. Spoiler alert - it turned out to be a bad LED. I'd read that it should briefly flash brightly, then stay on with a dim glow. Mine did neither. After confirming voltages, proper wiring, etc. I decided that I would try to force a DTC code to see if the MIL would light. I chose to unplug the TPS (throttle position sensor) cable at the throttle body to try to generate a DTC code. I figured if I was seeing a code on the scanner but the MIL was still not lighting, then I knew the problem was with the light itself. The problem is that my strategy worked a little too well. Sure enough, unplugging the TPS cable generated two DTC codes (P0122 - Throttle position sensor A circuit low input and P0223 - Throttle position sensor B circuit high input). However, rather than just generating two pending codes (which I was able to clear with my scanner), it also generated two "permanent" codes. You haven't heard of permanent DTC codes before? You're not alone. You can read all about them here:

https://www.bar.ca.gov/Industry/PDTC

Long story short - they are meant to prevent smog compliance fraud by not permitting the deleting of codes for certain key functions immediately before a smog check, and cannot be cleared with a scanner or by disconnecting the battery for 24 hours, or by any other means other than performing a "drive cycle" - a very specific sequence of driving the car at certain speeds and RPM's for specific lengths of time, to prove to the PCM that the problem has been corrected. This is a little tough to do when the body isn't even on the car yet.

No problem, I thought. I'll reach out to Ford Performance and explain my issue and they'll set me straight. They're very nice people, and after several phone calls and e-mails, they recommended that I send in the PCM to have it re-flashed to eliminate the permanent DTC codes. I FedEx'ed it over and they very quickly re-flashed it and returned it to me. Much to my chagrin, the permanent DTC codes are still there.

I then e-mailed Lund Racing to see if this is something that they could simply overwrite as part of the custom tuning process. They have never even heard of permanent DTC codes before, and have no idea if they can be overwritten. They are telling me I have a bad throttle body (I don't).

I am now working with Ford Performance again to see if they have other ideas on how to clear these codes. I'm guessing that they are stored in a separate dedicated memory that is not overwritten as part of the normal reflashing process. Still waiting to hear back on whether or not they can do anything.

Worst case - these codes will persist until such time as I can drive the car for long enough to be able to clear the codes. The problem is that the car runs very poorly at the moment, and definitely needs a custom tune to drive on the street, so I'll likely have to do a custom tune with these codes present, and then possibly have to re-do the tune once the codes are cleared.(?) I really have no idea, and I'm betting anyone at Lund that thinks they have an idea of what will happen probably doesn't either.


tl/dr (as the youngsters say) don't go trying to generate DTC codes, lest you get what you wished for.

[edwardb]

Excellent write-up John. Sorry to hear this problem is still persisting. A little surprised Lund isn't aware of permanent codes. Maybe that was just the specific tech you were speaking with? (Not that I should talk since I hadn't heard of them before either.) Based on a quick Google search, which I'm sure you've done, those are considered critical failures and the engine indeed is put into some type of limited throttle/failsafe mode. It's hard for me to imagine any type of custom tune would be very meaningful. At least based on any log file you would send them. Perhaps they have a generic initial custom tune, based on their experience with the crate motor in these cars, which would allow you to drive it enough to clear the codes. Good luck.

[JohnK]

Hi Paul. Yes, thank you for catching my typo on the second DTC code. I've corrected my post above. It's possible that it was just the one tech at Lund that was unaware. I don't have much experience with Lund but I've exchanged 8-10 messages with them through their support system so far. One frustration is that conversations get handed off from one tech to another so I find myself having to repeat key details to the next person. I wish there was a way to just have a quick phone chat but so far I have not been able to find any phone number to contact them.

I had the same thought regarding a generic initial custom tune to get me up and running, and I've asked them about this but haven't gotten a clear response as to whether this is possible or not. Your roadster config, for example, is very similar to my build with the only meaningful difference being that my headers have catalytic converters. For the moment I'm going to see if Ford Performance can help out, and then come back to Lund once I have some more direction from Ford. I'm sure it'll get sorted out one way or another. It's not the first obstacle I've run into in the build process ;). Everything is solvable.

[Joel Hauser]

I definitely feel your pain. DTC's and a faulty ECU left me in tears for months. I'm on my third ECU, which seems to be holding up after a couple years. Have you considered buying a rebuilt ECU with a stock tune from an aftermarket supplier like flagship 1? They program your vin into it so it should be compatible for emissions. It might get you going while you get your main ECU troubles worked out? (its easy for me to spend your money, right?)

[JohnK]

Update:

I heard from Ford Performance with the following response:

"Once the issue is resolved the code will delete itself out of permanent memory after a certain number of successful drive cycles."

Translation - there's nothing they can do about it.

I relayed this to Lund, and we all collectively shrugged our shoulders and decided we've give the custom tune a try and see what happens. I sent them the VCM suite info and stock file two days ago, and I received the baseline tune today based on my hardware configuration, and loaded it up. Straight away, the permanent DTC codes were gone. I started the engine and let it idle until it came up to temperature. Everything looked normal, and checking with a scanner afterwards still showed no DTC codes. So I hopped in and took it for a spin around the block (or two). It's immediately obvious that it's running much more smoothly, and the MIL is doing it's normal dim glow thing so I'm assuming that there are still no DTC codes. All seems OK for now. Fingers crossed.