MK7 2.4 RWD - ABS / ESP lights & No speedo

[Coley3159]

Hi all,

After cleaning the van (outside only not inside the engine bay) the ESP & ABS lights illuminated and the was no speed being registered or info on the central display and the hand brake light also remained on. When driving home the ABS & hand brake light went out and the speedo returned but the ESP light and lack on info on the display remained.

I plugged it into forescan and got the following DTCs:

- PCM U0121:00-2F - lost communication with ABS module
- OBDII U0121-P - lost communication with ABS module
- BCMii U0121:00-0A - lost communication with ABS module

I tried to clear the DTCs and all the lights came back on and the only one that cleared was the OBDii U0121-P.

I have quick look at the ABS sensors and nothing seems to be damaged.

Can i use forescan to check each individual ABS sensor?

Cheers

[braapday]

is the engine running properly? have you checked the fuses in the engine compartment box?
For abs and esp are R13-R20-R21, I'm assuming it's a euro 4 your transit seeing the dashboard

[Coley3159]

The engine seemed to be running fine on the way home. I checked F13, F20 & F21 visually and all looked ok. I will check F31 vehicle speed sensor and R5 ABS/ESP Relay when i get back from work. Are there any other fuses or relays to check?

[Coley3159]

The van is a 2011 euro 4 and it had two new YUASA 5000 batteries last January and all the tyres are the same brand and size.

I find it too coincidental that this isuue only occured after jet washing the van. Possibly i have got water in a abs sensor?

On my next day off work i will:

- Visually inspect ABS sensors & clean connectors
- Visually inspect reluctor rings & clean
- Continuity test on all ABS sensors (unless i can do this with Forescan?)
- Clean inner wing ABS earth point (doesnt look too bad compared to others ive seen)

Are there any other features i can use on forescan to aid me in diagnosing the issue?

Anything else to check?

cheers

[braapday]

yes sorry, I wrote the initials R by mistake instead of F.
Seeing the fuse and relay diagram I don't think there's anything else to check.
Can you connect to the PCM with forscan? Do you just have problems connecting with the ABS module?
Edit: if you can't connect to the ABS module, I doubt you can do individual sensor tests at the wheels, if that can be done at all.
Since the speedometer doesn't work either I would try doing a test on the BCM which from forscan seems possible

[andz327]

Bad earth's, broken wires from abs sensors , and faulty abs sensors can all cause no speedo and mileage ------- lines, usually when 2 or more sensors (or broken wires to sensors) are faulty,
Before replacing any sensors give the loom wires to the sensor wires a real close look for a cracked/split wire as they get very brittle especially around inner wing areas

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[Coley3159]

Had a chance to look at the van today. Quickly cleaned up the ABS earth point with electrical cleaner and a wire brush (the bolt is rounded so did it in place). I then checked all fuses and relays and everything looks good. Started the van and after 20 secs the ABS light went out but the ESP and ---- remained. I let the van run for 10 mins and then restarted and the ESP light went out and ---- turned back to numbers! I then plugged into Forescan and managed to clear the DTCs and everything seems to be back to normal. I haven't taken the van for a proper spin yet but drove back and forth on the drive to see if the dash lights came back and nothing did. I guess I got water somewhere it didn't like when cleaning the wheels and arches with a jet washer, last time I will be doing that! Im guessing its the earth point that's caused the issue and I will need to relocate these to fresh metal in the future.

[knobby1]

Had a chance to look at the van today. Quickly cleaned up the ABS earth point with electrical cleaner and a wire brush (the bolt is rounded so did it in place). I then checked all fuses and relays and everything looks good. Started the van and after 20 secs the ABS light went out but the ESP and ---- remained. I let the van run for 10 mins and then restarted and the ESP light went out and ---- turned back to numbers! I then plugged into Forescan and managed to clear the DTCs and everything seems to be back to normal. I haven't taken the van for a proper spin yet but drove back and forth on the drive to see if the dash lights came back and nothing did. I guess I got water somewhere it didn't like when cleaning the wheels and arches with a jet washer, last time I will be doing that! Im guessing its the earth point that's caused the issue and I will need to relocate these to fresh metal in the future.

Have a check of the front battery after the van has been sitting overnight...they're still working hard even when the van isn't running...they usually fail first.

Lord Knobrot

[andz327]

Not taking earth bolts out to clean faces does only one thing and that's wasting your time, they need to be cleaned under the bolt heads

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[Coley3159]

Went to move the van and the faults are back is back with the same DTC's

Not taking earth bolts out to clean faces does only one thing and that's wasting your time, they need to be cleaned under the bolt heads

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I agree! I was being lazy and didnt have anything to extract the rounded bolts. I have now brought a bolt extractor kit and will be removing the old rusty one, cleaning up the area and replacing them. I know they are 8mm heads, any idea what thread pitch?

When waiting for the bolt extractor to arrive i tried to clean both the wheel arch earths and the van didnt like it at all. I got a few news codes:

- P1796 - Can Control Circuit (Bus off)
- U0100 - Lost communication with ECM/PCM A
- U0001 - High Speed CAN Communication Bus

As well as an array of dash lights which flashed on and off including water in fuel, drive train, check engine and oil light.

After letting the contact cleaner dry out more i cleared and the new codes and now only have the orginal ABS/ESP lights with the codes:

- PCM U0121 - Lost communication with ABS Module
- BCMii U0121 - Lost communication with ABS Module

Im going to get these earths sorted forst and see if i can regain coms with the ABS Module.

[Coley3159]

Had a chance to look at the van today. Quickly cleaned up the ABS earth point with electrical cleaner and a wire brush (the bolt is rounded so did it in place). I then checked all fuses and relays and everything looks good. Started the van and after 20 secs the ABS light went out but the ESP and ---- remained. I let the van run for 10 mins and then restarted and the ESP light went out and ---- turned back to numbers! I then plugged into Forescan and managed to clear the DTCs and everything seems to be back to normal. I haven't taken the van for a proper spin yet but drove back and forth on the drive to see if the dash lights came back and nothing did. I guess I got water somewhere it didn't like when cleaning the wheels and arches with a jet washer, last time I will be doing that! Im guessing its the earth point that's caused the issue and I will need to relocate these to fresh metal in the future.

Have a check of the front battery after the van has been sitting overnight...they're still working hard even when the van isn't running...they usually fail first.

Lord Knobrot

I installed two new YUASA 5000 batteries last January and both checked out fine on the multi meter. They are topped up by the solar system install in the van as well.

[DanMK7uk]

I know they are 8mm heads, any idea what thread pitch?

Oh gosh

Pitch be about m5 / m6 - 0.8 mm - 1mm torque about 10nm

[Coley3159]

I know they are 8mm heads, any idea what thread pitch?

Oh gosh

Pitch be about m5 / m6 - 0.8 mm - 1mm torque about 10nm

Thanks, i meant i know that an 8mm socket fits but wasnt sure of bolt size and pitch.

[DanMK7uk]

Let us know how you get on. Cheers

[andz327]

Give all the wires from the abs a right good check for splits /broken wires , and check for any green guff at a split wire shown corrosion/short to ground etc, are all abs sensors reading ok?...
If any earth bolts snap just drill hole and use nut and bolt just make sure bare metal contact once all connected spray some zinc primer then paint to avoid more corrosion or grease if no paint

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