ABS Return Pump Sticking or Failure

[dayswaste]

"Now here's a little story, I've got to tell, about three bad brothers, you know so well. It started way back in history with Brake warning lamp, A.B.S. and T.C." - Beastie Boys


I've been slowly resolving issues with the three amigos since I've discovered it's a requirement for registration (I've recently moved across borders) and just hit a wall. I think the pump return motor attached to the modulator is stuffed and would like a nudge as to how to proceed.


The vehicle is a 1999 TD5 Defender with Wabco ABS and TC.

The fault returned by connecting a Nanocom to the ECU is as follows:

01-05
pump failure 3 (pump sticking)
001 times

The fault, thus warning lamps, can be cleared however the pump fails immediately on drive which activates the lamps again.

This is the only current fault, as all other faults have been rectified thanks to the good oil.


So, this may or may not be a good thing to do, but I took it on myself to run the pump using the Nanocom to see if the "sticking" could be cleared with a little use. I doubt it's been functioning correctly for a very long time, with the shuttle valve switches and sensor issues I've already resolved, Once activated I hear the pump return relay switching on and off multiple times and can feel the brakes wobbling the vehicle slightly, then the Pump return fuse link blows. Of course now I get a new fault code because the pump won't run with a blown fuse:

01-04
pump failure 2 (pump not running when actuated)
001 times

Replacing the fuse, I'm back to the sticking pump fault and repeating the activity leads to the same results.


A couple of questions:

Should I give in and find a replacement pump and modulator assembly, with recommendations for acquiring one, given their ridiculous price?

and

Should the pump be activating at all through simple driving? I was under the impression it would only activate under ABS operation? If this is so, then perhaps I still have another fault which is causing the ABS to activate without reason?

Any help appreciated while I read more about the operation of this system while it's no longer registered.

[Max Headroom 2.3m]

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.[bigsad]

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

(https://www.lrparts.net/srb500550-defender-abs-modulator-fits-up-to-end-2010.html)

[dayswaste]

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.

[dayswaste]

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.

[dayswaste]

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.

[Max Headroom 2.3m]

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

To save some serious coin![bigsmile]


It does sound like you have a wiring problem. Here (http://www.hummerknowledgebase.com/brakes/absmod.pdf) 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 (https://www.aulro.com/afvb/local_links.php?action=jump&catid=7&id=95) 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.

[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/pdf/815/000/430/815_430.pdf

Looking for a replacement modulator at the moment.

[djam1]

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/pdf/815/000/430/815_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 (https://www.jobsonelectronics.com/electronic-modules-components.php)

[dayswaste]

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.

[Scotty85]

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.

Mate keep us posted on how it goes!!

My Td5 has the ABS module failure too and I was considering the disco one as a replacement but was worried about the ABS firing on the wrong wheels when braking.

[shack]

I also believe they are the same modulator, the pipe connections all look to be in the wrong order though, creating concern that the wrong wheel will be braked, however I think they do work fine and that in conjunction with the piping change, the wiring is also different on the defender to allow proper operation.

Someone with half an HR and the wiring diagram should be able to confirm this, but I'm not doing it!

Cheers
James

[dayswaste]

Mate keep us posted on how it goes!!

My Td5 has the ABS module failure too and I was considering the disco one as a replacement but was worried about the ABS firing on the wrong wheels when braking.

Direct swap, no problems, don't change order of brake lines or wiring. Leave the Defender Lines as marked FL FR RL RR from left to right.

I tested operation using Nanocom to confirm each wheel responds correctly.

The WABCO sticker was identical:

WABCO 003 1999 ABS (year was different)
478 407 022 0

WARNING: Don't proceed without a Nanocom or equivalent to bleed the brakes and modulator.

Note: I replaced the unit without removing the right hand guard, but it's a tight squeeze,

[dayswaste]

I also believe they are the same modulator, the pipe connections all look to be in the wrong order though, creating concern that the wrong wheel will be braked, however I think they do work fine and that in conjunction with the piping change, the wiring is also different on the defender to allow proper operation.

Someone with half an HR and the wiring diagram should be able to confirm this, but I'm not doing it!

Cheers
James

I can confirm there are differences in the wiring because if you've already done the SVS wiring bypass, you'll find the colour of the cable different. Same operation but red instead of yellow. Because I'm not changing the wiring or the Wabco ECU, I didn't spend much time comparing the two.

Another note is the diameter of the brake lines are different, so if you try to swap lines around to suit the Disco, you'll be in all sorts of pain.


I should also note that I'm not a brake or hydraulic specialist so don't take my word as fact. I have tried to be as accurate with my findings as possible but these are your brakes, don't kill people, see a specialist.

[shack]

For sure...