Thread: ABS Return Pump Sticking or Failure

I am not familiar with this fault code but I feel your pain. We bought a 2003 TD5 fender last year with what appeared to be a leaking master cylinder. Turns out it was the ABS modulator....no problem, just replace the shuttle valve and the two seals. When I removed and tested the valve assembly, it was fine and then notice brake fluid weeping from the solenoid block above. I gingerly split the solenoid block and found one of the output solenoids was badly corroded and had parted it's casing.

To cut a long story short it was RS and I was now faced with the dilemma of buying a new ABS modulator (eye-wateringly expensive!) or source a good secondhand one (not that cheap and hard to find as you need to have the Defender specific model - Disco ones have different output pipe layout). So I bit the bullet and bought a new one. If you need one, the cheapest I found was here

Thanks for the link Martin.
My understanding is a Disco module can be used, you just ignore the printed order and use the existing defender locations. I haven't tried this yet but my understanding would be that the Wabco ECU is programmed differently between the disco and fender while the modulater is essentially the same.

I've tested out the wiring looking for a current drain and I'm afraid the current drain I'm experiencing is in the return pump motor.

Just to clarify, through some trial and error testing which is all i really do with everything, The fault is not returning on drive, in fact to create the fault I need to slide around on gravel, braking hard a few times, before it shows up. The other time it shows up is on ignition start, which I assume is a self test procedure which is failing. Disconnecting the Wabco ECU from the return pump relay circuit results in faults relating to exactly that:

02-02
pwm signal failure from engine ECU

Or unplugging the pump motor from the wiring:

01-03
pump failure 1 (monitor line)

I don't know why I put myself through all this.

It's like expanding the equation to the point of being able to simplify it.

Originally Posted by dayswaste

I don't know why I put myself through all this.

To save some serious coin!


It does sound like you have a wiring problem. Here is an article by a guy who thought he had a shuttle valve problem but turned out to be a faulty soldering joint where the shuttle valve plugged into. He also stripped down the modulator with pump completely and explains how the system works. I don’t know if you have a copy of the Wabco ABS manual but you can get a copy here if you need it.


I think you are right and that the modulators would be the same unit between Disco and Defender as I would think it unlikely that model specific units were made. For them to change the label on top is easy. I had considered trying a Disco modulator but couldn’t figure out a way to validate if it was working correctly at the time. Thinking about it now, if the only difference between the two modulators is the label on top then a way that the operation of the different wheel calipers could be achieved between the Disco and Defender is by changing the pin arrangement of the plug that connects to the modulator. If this is the case then a Disco modulator plugged into a Defender may behave like a Defender modulator. Perhaps a way to verify this would be to do a Nanocom Defender power bleed and see if is squirts out of the appropriate caliper bleed nipple.


I had decided against trying any of these hacks though as I didn’t want to risk compromising my insurance if I got it wrong, hence why I bought a new Defender specific one.

Thanks Martin,

I've previously bypassed the internal circuit fault with the external wiring of the Shuttle Valve Switch to try to clear the Shuttle valve faults, it wasn't the problem and only cleared with a replacement Shuttle Valve Switch.

The electrical faults I've posted where all self administered while investigating it's operation. I've confirmed it's not a wiring fault as a result.

Here's a good document while we're sharing info: http://inform.wabco-auto.com/intl/pd...30/815_430.pdf

Looking for a replacement modulator at the moment.

Originally Posted by dayswaste

Thanks Martin,

I've previously bypassed the internal circuit fault with the external wiring of the Shuttle Valve Switch to try to clear the Shuttle valve faults, it wasn't the problem and only cleared with a replacement Shuttle Valve Switch.

The electrical faults I've posted where all self administered while investigating it's operation. I've confirmed it's not a wiring fault as a result.

Here's a good document while we're sharing info: http://inform.wabco-auto.com/intl/pd...30/815_430.pdf

Looking for a replacement modulator at the moment.

Doesnt have to be a big crisis if you speak to these people they can rebuild your unit.

Electronic Modules and Components Melbourne, Melbourne CDB, Carlton, Fitzroy | Jobson Electronics

Thanks Chatterbox, good to know, I'd definitely consider it if I was in Victoria. May even consider it again in the future.

I've gone with replacing the modulator with a second hand one from a Discovery. Straight swap ignoring disco sticker, no problems. All wheels activate in correct order.

Once roadworthy and registration is sorted I'll have to try out this fancy ABS and Traction control business that I haven't worried about until now.