Service Advancetrac. Forscan shows U0401-20

[michiganave]

I just got Forscan today to help sort out my "service advancetrac" warning. Has gone off a few times over the last few months. Then this week went off 5 times on one drive, stayed on, then the gas pedal stopped working and I had to pull off the road. Turned the vehicle off, turned on, drove home normally. I bought an OBDLink EX USB and ran Forscan and the only DTC is U0401-20.

Dtc in abs. U0401-20
Invalid or missing can data from the pcm.

Status
-Previously set dtc. Not present at time of request.
-Malfunction indicator lamp is off for this dtc

Module
-Antilock braking system

So what is next? I couldn't find this code on the forum.

I tend not to take the vehicle to the dealer given how modified it is. 2014 on 37s with Icon Stage 4 suspension, Roush Supercharger with custom tune, bumpers, lights, cameras, the entire interior was pulled for sound deadening and a custom stereo. I haven't done any recent modifications before this issue came up.

 

[Canuck714]

I've been down this road before, its not fun tracking it down.
The Can-Bus system in these trucks is a two-way communication pipeline between modules. Any interference in the communication causes all kinds of Codes, CEL, faults, etc.
Couple things that could possibly be causing the issue:
FUSE 27.. I chased so many things trying to sort my truck and it all came down to a melted socket at Fuse 27. The fuse was fine, but the socket deteriorated just enough to allow electrical interference to enter the can-bus. If I turned on upfitter switch 3&4 the truck would shut off. Even when it was completely disconnected. Ford had no idea how..lol
I installed the jumper to bypass Fuse 27 and all is good.
WHEEL SPEED SENSOR.. I have seen a bad wheel speed sensor kick in the Hill Decent Fault code before.
HIGH MOUNTED BRAKE.. Water ingestion in the 3rd brake light can cause a short sending interference and triggering Hill Decent.
BODY GROUNDS.. There are several ground locations under truck as well as in engine compartment. Clean grounds and coat with Die-electric grease. Also check the ground in passenger footwell that is on the Body Control Module. This has caused issues in the past. There is one on drivers side footwell as well.

Hope some of this helps you find the issue.

 

[FordTechOne]

With only DTC U0401 is continuous memory, I would suspect that the other DTCs cleared themselves once the fault went away.

I would recommend keeping your laptop with you and as soon as the fault occurs, pull over and retrieve DTCs.

 

[myersroofer614]

Ty. I'm having issues

 

[michiganave]

With only DTC U0401 is continuous memory, I would suspect that the other DTCs cleared themselves once the fault went away.

I would recommend keeping your laptop with you and as soon as the fault occurs, pull over and retrieve DTCs.

I checked while it was actively having the fault. Said nothing in addition.

Remains really random when it decides to throw issues. Most of the time is just fine.

Might be time to go to a dealer? Not my typical move given how modified the vehicle is. But the aftermarket tuning shop that has previously done work on the vehicle was not very helpful and did zero diagnostics other than drive the truck around and say it didn't fault while they drove it...

 

[FordTechOne]

I checked while it was actively having the fault. Said nothing in addition.

Remains really random when it decides to throw issues. Most of the time is just fine.

Might be time to go to a dealer? Not my typical move given how modified the vehicle is. But the aftermarket tuning shop that has previously done work on the vehicle was not very helpful and did zero diagnostics other than drive the truck around and say it didn't fault while they drove it...

Dealer is not going to be able to help if it’s only setting U0401. The only diagnostic direction for that code is to pull PCM DTCs and diagnose from there. If the PCM isn’t setting DTCs, there may be something in the tune that is outside of the parameters that the ABS Module is looking for. Meaning the PCM is not flagging a fault, but when the data is sent to the ABS Module it’s being interpreted as invalid data.

 

[michiganave]

Dealer is not going to be able to help if it’s only setting U0401. The only diagnostic direction for that code is to pull PCM DTCs and diagnose from there. If the PCM isn’t setting DTCs, there may be something in the tune that is outside of the parameters that the ABS Module is looking for. Meaning the PCM is not flagging a fault, but when the data is sent to the ABS Module it’s being interpreted as invalid data.

Helpful. Though not sure where to go from here. The vehicle is randomly and dangerously disabled when the advancetrac warning goes off. Goes into this limp mode where I can’t even use the gas pedal! Not good on the freeway. Though sometimes it just throws the warning and acts normally. And most days no warning and drives fine. What would you suggest if not a dealer for diagnostics? I’ve gotta get this fixed.

 

[FordTechOne]

Helpful. Though not sure where to go from here. The vehicle is randomly and dangerously disabled when the advancetrac warning goes off. Goes into this limp mode where I can’t even use the gas pedal! Not good on the freeway. Though sometimes it just throws the warning and acts normally. And most days no warning and drives fine. What would you suggest if not a dealer for diagnostics? I’ve gotta get this fixed.

Have you self-tested both the PCM and ABS Module immediately after the fault occurs? I believe ForScan has that capability; self test checks all module inputs and outputs and will set DTCs for anything out of range.

There is almost no scenario where the engine will de-rate and the PCM won’t set a corresponding DTC, which leads me to suspect the aftermarket tune may be a contributing factor. Or root cause.

 

[michiganave]

Have you self-tested both the PCM and ABS Module immediately after the fault occurs? I believe ForScan has that capability; self test checks all module inputs and outputs and will set DTCs for anything out of range.

There is almost no scenario where the engine will de-rate and the PCM won’t set a corresponding DTC, which leads me to suspect the aftermarket tune may be a contributing factor. Or root cause.

No, I had not been running self tests. Just checking the main DTC. which is what is reporting the U0401-20 in ABS.

I ran self tests just now. There is PCM engine off. PCM engine on. And ABS. I got something about air conditioning that seems irrelevant. But I had not been running these self tests at the time of the error. I suppose that could be useful next time?

 

[FordTechOne]

No, I had not been running self tests. Just checking the main DTC. which is what is reporting the U0401-20 in ABS.

I ran self tests just now. There is PCM engine off. PCM engine on. And ABS. I got something about air conditioning that seems irrelevant. But I had not been running these self tests at the time of the error. I suppose that could be useful next time?

Yes, as soon as the fault occurs run a self test on the PCM and ABS Module and see what you get. The A/C DTC is likely just an informational code for “outside of self test parameters”.