P38A ABS issue - fault codes

So I've been having a long term ABS issue. When you drive and use the brake pedal it pulses and activates the ABS. It does this most applications of the brakes, at all speeds and conditions.

The vehicle has had quite a few bits done to solve this. My Nanocom won't talk to the ABS unit. Although a local specialist has used their ex dealer diagnostic machine too.

No warning lights. But using another diagnostic tool I'm seeing these fault codes.

From the main ECU/OBDC:


Specifically from the Wabco D:





Does anyone know what could cause these, or more importantly how to fix them?

And on this note, do you think that these codes are likely related to the issue I'm having?

The vehicle is largely underivable at the moment, as braking is inconsistent and you don't know when it will stop. I've pulled the fuse for the ABS which makes it drivable, but of course not a lot of use for an MoT.

300bhp/ton said:

So I've been having a long term ABS issue. When you drive and use the brake pedal it pulses and activates the ABS. It does this most applications of the brakes, at all speeds and conditions.

The vehicle has had quite a few bits done to solve this. My Nanocom won't talk to the ABS unit. Although a local specialist has used their ex dealer diagnostic machine too.

No warning lights. But using another diagnostic tool I'm seeing these fault codes.

From the main ECU/OBDC:

Specifically from the Wabco D:

Does anyone know what could cause these, or more importantly how to fix them?

And on this note, do you think that these codes are likely related to the issue I'm having?

The vehicle is largely underivable at the moment, as braking is inconsistent and you don't know when it will stop. I've pulled the fuse for the ABS which makes it drivable, but of course not a lot of use for an MoT.

Click to expand...

ABS ECU's are known to fail. Fix that first and get comms working. If you still have a problem, it's likely to be the modulator block.

Datatek said:

ABS ECU's are known to fail. Fix that first and get comms working. If you still have a problem, it's likely to be the modulator block.

Click to expand...

Comms work with 2 out of 3 diagnostic tools. Hence the codes in the screenshots. But no idea why the Nanocom doesn't work with it. Wouldn't know where to start with fixing this bar buying a used one (which seems hard enough) and reasonably pricey as a trial and error fault finding exercise.

What is the modulator block? Is there a part number I should be looking for? Thanks.

300bhp/ton said:

Comms work with 2 out of 3 diagnostic tools. Hence the codes in the screenshots. But no idea why the Nanocom doesn't work with it. Wouldn't know where to start with fixing this bar buying a used one (which seems hard enough) and reasonably pricey as a trial and error fault finding exercise.

What is the modulator block? Is there a part number I should be looking for? Thanks.

Click to expand...

I seem to remember that there have been problems with the Nanocom and ABS, might be wrong on that though.
If you are confident that the diagnostics are P38 compatible and not giving false codes, then the fault is in the modulator block. that's the big lump very expensive under the brake fluid reservoir with the brake pipes coming out of it.
The brake switch needs looking at and personally I would be having the connector off the ABS ECU to look for corrosion, these being the 2 easiest and cheapest things to fix if there is a problem with them.
Bonne chance.

Datatek said:

I seem to remember that there have been problems with the Nanocom and ABS, might be wrong on that though.
If you are confident that the diagnostics are P38 compatible and not giving false codes, then the fault is in the modulator block. that's the big lump very expensive under the brake fluid reservoir with the brake pipes coming out of it.
The brake switch needs looking at and personally I would be having the connector off the ABS ECU to look for corrosion, these being the 2 easiest and cheapest things to fix if there is a problem with them.
Bonne chance.

Click to expand...

Thanks. tbh I'm not confident on anything...

I don't think the Nanocom has ever worked with the Wabco since owning the Nanocom. The ABS issue is much more recent, so I'm hoping it isn't the issue. pscan is designed for Rover cars, but claims to do the p38 and has Wabco as a selectable item in the menu.

Do you think that this code would cause the symptom I'm getting though? I see under Disco 2 there is a shuttle valve repair kit, is there such a thing for the p38?

So far it has had lots of new sensors and a new accumulator.

300bhp/ton said:

Thanks. tbh I'm not confident on anything...

I don't think the Nanocom has ever worked with the Wabco since owning the Nanocom. The ABS issue is much more recent, so I'm hoping it isn't the issue. pscan is designed for Rover cars, but claims to do the p38 and has Wabco as a selectable item in the menu.

Do you think that this code would cause the symptom I'm getting though? I see under Disco 2 there is a shuttle valve repair kit, is there such a thing for the p38?

So far it has had lots of new sensors and a new accumulator.

Click to expand...

An Australian guy does, or used to do, replacement valves for the modulator, I don't know if he is still around, otherwise it would be a replacement from a breaker but I'd still look at the connector to the ABS ECU as it's prone to get wet where it's located. It might even be worth a full brake bleed as old fluid does cause problems.

300bhp/ton said:

So I've been having a long term ABS issue. When you drive and use the brake pedal it pulses and activates the ABS. It does this most applications of the brakes, at all speeds and conditions.

The vehicle has had quite a few bits done to solve this. My Nanocom won't talk to the ABS unit. Although a local specialist has used their ex dealer diagnostic machine too.

No warning lights. But using another diagnostic tool I'm seeing these fault codes.

From the main ECU/OBDC:

Specifically from the Wabco D:

Does anyone know what could cause these, or more importantly how to fix them?

And on this note, do you think that these codes are likely related to the issue I'm having?

The vehicle is largely underivable at the moment, as braking is inconsistent and you don't know when it will stop. I've pulled the fuse for the ABS which makes it drivable, but of course not a lot of use for an MoT.

Click to expand...

MartyUK has had some success with the Wabco D. He's not been seen since the pandemic started. He has his own forum somewhere and he's MartyNZ on RR.net.