Haldex Fault Indication

Haldex controllers used on VW group 4 wheel drive systems provide outputs to the ECU for diagnostics (e.g. Haldex clutch pump failure) However unlike some other manufactures using Haldex controllers, a fault does not bring up a warning light on the dashboard (e.g. Ford Kuga). Such a fault indication could save considerable money otherwise spent on expensive repairs (e.g. destroying the pump because of low oil flow rates) and potentially avoid some dangerous situations where the driver mistakenly believes they have 4 wheel drive but in fact they are actually only 2 wheel drive.

The query is therefore would it be possible to add a code to say for example the existing traction control light such that a fault in the Haldex registered in the diagnostics would bring up a warning?

No, this is a function in the control module which cannot be altered. However, your "expensive repairs" situation could be solved in a very simple way by performing a complete VCDS Auto-Scan prior to any repairs and it would show said code just fine.

Except when it doesn't and the Haldex/diff blows up at 70mph with no warnings.

Yep, happened to me and my 2010 Tiguan following a 75k diff service per the book. Did the pump fail? No one really knows... the result from the tear down of the diff is that the input shaft pinion bearing failed causing catastrophic failure of the diff. There were no fault codes in the Haldex controller before or after the event. I've asked for a write-up on the failure along with photos. I think all would like to see.

My point: the fault information in the Haldex controller will not be the end all. The Haldex is known to be a weak unit (based on VW TSBs) and VW recommends replacement of the pump, filter and fluid before 75k if the customer notices a problem. Sounds to me like they know they have flawed units. Why then do they not recall and replace pumps, being proactive and reducing the risk to their customer?

When the diff blew, there is no telling how that failure may have manifested itself. Had it locked a wheel, I might not be here to report any of this. Surrounded by tractor trailers on I-81 in the mountains of Virginia - who knows from what ditch I might have been pulled.

The Haldex fails are a very real safety concern in my mind having lived one. Far worse than NOX emissions from 18k diesel cars each year in the USA. I guess someone has to die before a recall will be generated.

Thanks for the responses.

The basic problem is that the VW group, unlike Volvo etc, do not recognise that the Haldex units have filters and / or strainers, depending on generation, that can and do block. This either lowers the oil pressure in the system so that the unit no longer functions, but you wouldn't notice until the vehicle needed to go into 4 wheel drive or in the worst, but not uncommon cases the pump gets starved of oil and consequently fails.

Importantly a low pressure will flag up a fault code, and in the case of say the Ford Kuga - but not VW - will bring up the light I mentioned on the dash, so that a change or clean of the filter and strainer can be undertaken before damage is done to the pump or a dangerous situation arise where 4 wheel drive is required but is not actually available. Trouble is that the mileage at which this problem occurs seems to be very variable so unless, in the case of VW group vehicles, you ran a VCDS auto-scan on a regular basis you might not catch the problem before it becomes very expensive and hence my initial query.

Sebastian: When you say "this is a function in the control module which cannot be altered", excuse my ignorance but which module are you referring to?

Bruce: I have to wonder if the pump bearing failure was a result of oil starvation itself a result of a blocked filter and/or strainer.

Upsidedown said:

Bruce: I have to wonder if the pump bearing failure was a result of oil starvation itself a result of a blocked filter and/or strainer.

Click to expand...

In Bruce's case, the failure was not actually the Haldex, but the differential behind it. We went to see (and pay our final respects to) the the disassembled unit today. As you're probably aware, the differential is in the same housing as the Haldex, but is separately lubricated. The longitudinal bearing at the input to the rear differential is what failed in Bruce's case. His Haldex unit itself, extracted from the housing, looks to be OK.

-Uwe-

Upsidedown said:

Sebastian: When you say "this is a function in the control module which cannot be altered", excuse my ignorance but which module are you referring to?

Click to expand...

I'm pretty sure what Sebastian is trying to say is that there's no practical way to get a VAG instrument cluster to report fault conditions that VAG didn't design the software in it to report, nor is there any practical way to get a Haldex control module to remotely turn on a light if such functionality wasn't designed in from the start.

-Uwe-

Uwe: Thanks for the clarification re which of Bruce's Tiguan components failed. As an apparently separate issue, do you know what the Haldex pump filter and/or strainer looked like as a matter of interest?

On the topic of the Haldex, again please excuse my ignorance, if there is a problem with say the Traction Control a message is logged in the ECU(?) and the software then switches on the relevant warning light. So if the ECU(?) is capable of logging a failure report from the Haldex would it be a matter of writing an equivalent software instruction to switch on pretty much whichever dash warning light you chose. Easier said then done perhaps, which I take it is what you are saying, but then I'm a vehicle software dummy.

Upsidedown said:

So if the ECU(?) is capable of logging a failure report from the Haldex would it be a matter of writing an equivalent software instruction to switch on pretty much whichever dash warning light you chose.

Click to expand...

In theory yes, but since the software is owned and copyrighted by VAG, it is VAG that would need to make the change.

All diagnostic tools can only report the errors that VAG deem necessary to implement in their software, so it's VAG you need to be lobbying not diagnostic tool developers.

Upsidedown said:

Uwe: Thanks for the clarification re which of Bruce's Tiguan components failed. As an apparently separate issue, do you know what the Haldex pump filter and/or strainer looked like as a matter of interest?

Click to expand...

The Haldex and diff had been serviced two weeks prior to the fail. In that service, all oil was changed and the filter was also changed. There was no sign of oil sludge or restriction in the Haldex or in the diff.

In my case, there was a bad bearing. At 83K miles, that bearing should not have failed. Had to be a defective part.

One might argue that given the failure, when the unit was serviced, the tech should have seen metal particles... we talked a little about that and did not come to a conclusion that the fail was well in progress before the service. We can make an argument that the fail occurred after the service and all wear came after... Bottom line, the bearing was bad from day one.. A bearing for a part like this should run lots of miles. The other bearings do not show any signs of wear or trouble.

I am going to post the photos so others can see. I hope to do so today.

Here is a link to an album showing the diff:

https://photos.app.goo.gl/RQD51p38GGZ5KXZT8

Didn't intend to hijack your thread...

Discussion here is about getting fault information from the Haldex to show on an instrument cluster... Let's go back there...

Upsidedown said:

As an apparently separate issue, do you know what the Haldex pump filter and/or strainer looked like as a matter of interest?

Click to expand...

Here's a random video with a filter change and filter dissection:


There are lots of other Haldex Service videos on YT.

-Uwe-

Bruce: Diff bearing is certainly not a pretty picture !

You note that the Haldex and diff had been serviced two weeks before the diff failure. A query but not related to the diff failure. When the Haldex was serviced was just the oil changed or the oil and filter (if it has one) and / or the strainer cleaned? If so did you request that this was done or did the servicing agent have it down as part of the service? I ask the question because VW in New Zealand and the UK do not recognise that there is a filter and / or strainer in the unit. Hence they are not cleaned resulting in unit failure.

Uwe: Sorry. Think we were talking at cross purposes. What I meant was did Bruce's Haldex unit (i.e. filter and/or strainer) look clean? Bruce has now however answered that query.

PetrolDave: I agree that the solution to my original query is a software (i.e. not diagnostic) issue but I was just hoping, given the amazing amount of technical know how on this forum, that there may be someone with the skills to write the code. Probably asking the impossible - unless there is a 12 year hacker following the forum!

Upsidedown said:

PetrolDave: I agree that the solution to my original query is a software (i.e. not diagnostic) issue but I was just hoping, given the amazing amount of technical know how on this forum, that there may be someone with the skills to write the code. Probably asking the impossible - unless there is a 12 year hacker following the forum!

Click to expand...

Access to the source code would be extremely difficult so it would need someone with more time than sense to reverse engineer the object code - like you say, a 12 year old hacker

But then, would you want hacked code controlling your Haldex? I know I wouldn't, especially given what happened to Bruce

PetrolDave said:

Access to the source code would be extremely difficult so it would need someone with more time than sense to reverse engineer the object code - like you say, a 12 year old hacker

Click to expand...

Not just the Haldex. Getting it to report a problem would only be half the battle. You'd also need a means of displaying the report, which would likely involve modifying the instrument cluster's software as well, and instrument clusters tend to be quite model-specific.

PetrolDave said:

But then, would you want hacked code controlling your Haldex? I know I wouldn't, especially given what happened to Bruce

Click to expand...

First, let me repeat: Bruce's failure had nothing to do with the Haldex itself; it was a bearing in differential behind the Haldex.

Second, there are people out there who modify the software in the Haldex modules for more "performance", but I assume they just tweak maps that determine under what conditions the clutch engages, which is a far cry from adding code that would communicate fault data the instrument cluster.

-Uwe-

Thanks everybody for all the input. Looks like its not possible

PS Then again perhaps I should talk to the Russian or the Chinese spy agencies. They seem able to hack anything!