Best way of diagnosing haldex fault?

[slowcoach3]

My haldex isn't working, I have done enough search's to be sick of reading about haldex issues so if we compile a definative thread on finding out what causes the issues and any fixes then we can get it made a sticky and save painful future searching and repetative questions?! I've scanned my car and no codes come up on the haldex ecu, so it must be mechanical, anyone have any good places to start?

 

[<tuffty/>]

By no faults do you mean no communication? what are you scanning with as not all generic scanners will pick up haldex issues...

VCDS is the only tool worth using in this case...

If its not working there will be a fault code of some description or at the very least a no communication error...

Typical things to check are the earth strap as I have seen more and more of these corroding (including my own recently), plug at the back of the diff as the pins corrode (Bill has posted a thread about this), rear end feels like its dragging when manouvering at low speed... this is due to the haldex clutch plates sticking and this can be the result of infrequent oil changes meaning the hydraulic system behaves irratically or because the car has been run on a dyno without the fuse being pulled... pump could have gone, hydraulic fluid not changed and not enough pressure to be able to engage the clutches...

You can do a haldex pump test by going to module 22 AWD and checking fault codes... I believe this cycles the haldex pump and you should hear in run briefly...

<tuffty/>

 

[S3Zek]

Just had this with my mates one, had no codes but didn't work,
Checked all above^^ and no different
But when testing the cycle on the pump it just made a clonk, replaced pump as all was good.

 

[S3Zek]

Not cheep from Audi tho 400 smackers.... So got a second hand one.

 

[slowcoach3]

I'm using vcds shareware, its communicating with the haldex and says theres no fault codes. The only earth straps I can find on my prefacelift are under the battery and engine/gearbox strap and they are all ok. I'll try those blocks in the morning, I can't do an output test with shareware unfortunately! The car has been on rollers recently but had the fuse pulled. Theres no locking from the rear just a lot of spinning from the front and torque steer...great after a remap!

 

[<tuffty/>]

Obviously not looking in the stickies then

http://www.audi-sport.net/vb/a3-s3-...working-no-communication-etc-look-inside.html

<tuffty/>

 

[S3Zek]

My mates pre one never had one eather but it has the bolt on the under side just above the rear diff on pas side so made one for it anyway.

 

[slowcoach3]

Damn it tufty! Ok, I didn't check the stickies., i'll be having a good read of that when I get home and off my annoying phone. Good idea making a strap...i like that. Pats3poa has said I can try his spare controller to see if that fixes it but it seems like a hell of a performance just to see if something works or not, gotta be an easier way0

 

[slowcoach3]

Tufty, I feel better now, I had read that already! I did as advised and checked AWD module on vcds again and this time I had two codes, first one is 00526 which is brake light related, don't know why as everything is working back there! Second code is a challenge though, code 01155. It doesn't appear on ross tech wiki. Had a bit of a google and the common consensus is that it relates to pre-charge pump? Does anyone have any more info to add to this? I'm not keen to order a pre-charge pump at great expense and find its not that.....
Any info greatly appreciated

 

[S3 Sly]

I have the same issue, only front drive. I got the break pedal switch fault also, the switch is linked to a few things, not just break lights. I replaced it and it made no difference. I also checked the plug and changed the oil and haldex filter.

Most of the posts I have read the fault seems to be precharge pump. Not sure if you can strip it down and carry out a fix.

 

[slowcoach3]

What i'd like to know is which part of the haldex system you need to replace to fit a new clutch? Is it in the diff? It seems much easier to fit a new diff than fix the clutch!

 

[<tuffty/>]

What i'd like to know is which part of the haldex system you need to replace to fit a new clutch? Is it in the diff? It seems much easier to fit a new diff than fix the clutch!

The Audi TT Forum :: View topic - Rear Diff Haldex Dissection After Diff Was Destroyed

<tuffty/>

 

[slowcoach3]

Cheers tufty, new diff it is then! Am I right in thinking that as my car doesn't have esp the new diff must also be from a car that doesn't? Cheers

 

[<tuffty/>]

Cheers tufty, new diff it is then! Am I right in thinking that as my car doesn't have esp the new diff must also be from a car that doesn't? Cheers

Diff should be the same but the haldex controller maybe different... sorry but don't know what the difference is... I think there was another member on here that posted up on a similar thread recently that had the same issue... Welly has also tried fitting a different haldex controller... I think the gasket setup is different too...

Sorry but not done one as yet so can't say for sure

<tuffty/>

 

[S3Zek]

Still think you should try and get to someone to do an cycle test, it should sound like a slow running fuel pump, or try someone elses pump maybe. If your anywhere near me your welcom to use my vcds or I can test it for you.

 

[slowcoach3]

Thanks mate, where are you based? I'm in Devon, the middle of nowhere!!! I'm going to change the filter and oil and see if that makes any difference, its worth a go I suppose. My first thought is pre-charge pump, when I scan the awd module on vcds there is no noise from the haldex/diff area at all so that might be logical, I can't find one for sale anywhere though so I'll ask TPS tomorrow when I get my filter etc, I'm not expecting a cheap fix!
Cheers Tufty, the clutch and gearbox center in Exeter do alot of haldex jobs and they're first thought is clutch in the diff, 170 notes to diagnose it so it'd be cheaper just to buy a diff, as long as esp isn't a problem I may have found one....

 

[S3Zek]

Unless your up for long drive I'm prob near 300 miles from u mate I'm afraid, im just outside of Newmarket suffolk. U tried asking people on eBay who are braking them even?

 

[slowcoach3]

Yeah that might be a bit of a trip! I've asked most of the people breaking Haldex cars and no joy yet but I've been going at it with vcds and had a temporary break through.... Found a new nasty code, 01324 awd control module no comms-Intermittent. Cleared this and a brake light code, took it for a heavy footed drive and awd works. Car feels amazing so solid! No codes when I got home but after doing a shed load of reading on this I'm not expecting such a simple fix to be long term but its good to know the whole system isn't knackered, just got to find out which bit is on the way out!!!!

 

[ceS3r]

I'm having this problem with my S3. I have no rear traction. Logged on 22 - AWD and it appeared brake light switch implausible signal, replaced the switch, the code is gone but still have the problem. I also have my Brake Pads Worn yellow light on DIS and this is because the wire from the pad sensor broke, just checked, but I don't know if that could make the haldex doesn't work? When I log on AWD I hear no sound at all, so the pump is not working I think. I checked the earth strap and was there but didn't checked if it was good connected or something. When I try to clear the codes from 22 - AWD it says something about comunication error. Could this be the Earth Strap?

 

[Av4nt]

Those of us that arent in the know...what is a haldex?

 

[Vex182]

Those of us that arent in the know...what is a haldex?

Haldex is the company that make the multi-plate clutch that makes the S3/TT a 4wd. It's reactive on these cars so they usually drive around as pretty much just fwd and the rear comes in when it detects wheelspin from the front.