# Haldex Control Module-Need Replacement-HELP!



## jsmBora1.8T (Feb 23, 2003)

My mechanic said I need to replace my Haldex Control Module on my 2001 Audi TT 1.8T Quattro Coupe. Car has only 26,000 miles on it. It is always garage kept etc. Very upset that the module has gone bad.

He provided me with the part Number (02D 900 554C). We are having problems finding a replacement.

Does anybody know of anyone who has them for sale or if there is another Haldex Control Module that will work? We have been searching the internet with no luck. Someone suggested the Blue Haldex.

Thanks fir any help you can provide


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## asiwa (Dec 18, 2014)

Unfortunately the controllers can go bad as a result of many factors - one being age - and some of the earlier ones tended to be less reliable.

Haldex Blues are impossible to find and are generally overpriced when you can find them. They also offer a minimal upgrade over stock for the money, and all of them will be used. All of the new factory controllers have been used up too, so any replacement you find will be used to a point. 

The easiest solution is to do a search on car-part.com if you are in the US. Select the make/model/year and then choose "Electrical" for the category and "Computer (non engine)" for the subcategory. After you put your zip code in, you'll get a list and you want to choose "Transfer Case, (rear carrier mounted)" and the results from that should all be Haldex controllers. Any controller from a MKI TT will fit on your car - regardless of year - and work as intended. 

Prices can range from below $75 to over $200, and details can sometimes be sparse. Some breakers have pictures of their parts but most do not, so if you or your mechanic are in doubt give the breaker a call and ask about the condition of the part and the car it came off of. You want to get a controller off a car with as few miles as possible and with a harness that is fully intact; sometimes they just cut the controller off by the connector and you will definitely be unhappy if you get one of those.

Let us know how it works out!

EDIT: By the way, is your mechanic absolutely positive that the controller is bad? I find it difficult to believe that it went bad on a car with such low miles that has always been garaged. The cargo pump could have gone bad as well, as that is a much more common failure point.


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## jsmBora1.8T (Feb 23, 2003)

You mention the Cargo Pump may need to replaced.

When driving the car it wants to pull to the left and feels like the brakes as being applied. Does this sound like the result of a bad cargo pump?


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## asiwa (Dec 18, 2014)

The pump is related only to the Haldex and would not affect drivability except for rear-wheel grip in bad driving conditions. What you are describing sounds steering/brake related. Best to ask your mechanic about this while he still has the car.

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## jsmBora1.8T (Feb 23, 2003)

OK. Thanks for the info.

One person was telling me it could be the longitudional accelleration sensor.


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## B1-16V (Aug 5, 2002)

Do you know if the car is activating the rear wheels at all? 

Slip or no slip in the rain?


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## B1-16V (Aug 5, 2002)

Not sure this is your issue with your low miles, and I think several of us are wondering if you even have an AWD issue at all, but maybe this might help...

https://forums.vwvortex.com/showthread.php?9323075-Haldex-Controller-teardown-and-fix


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## jsmBora1.8T (Feb 23, 2003)

Car is really never driven in the rain so I can't answer your question. When it was driven in the rain I never felt that the wheels were spinning.

My mechanic disconnected the Haldex Controller Unit. I have driven it and the pull to the left and feel of it trying to braking constantly has gone away. Can anybody confirm if you leave the HCU disconnected it will not hurt the car? Car is driven less than 3,000 miles a year.

I looked into purchasing a refurbished unit through Auto ECMS. However the unit will need to be reprogrammed. I'm wondering if that has to be reprogrammed by a dealer or my mechanic. It's my understanding the Audi dealers programming is exclusive to them. Can anybody shed any light on this?


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## asiwa (Dec 18, 2014)

jsmBora1.8T said:


> Car is really never driven in the rain so I can't answer your question. When it was driven in the rain I never felt that the wheels were spinning.
> 
> My mechanic disconnected the Haldex Controller Unit. I have driven it and the pull to the left and feel of it trying to braking constantly has gone away. Can anybody confirm if you leave the HCU disconnected it will not hurt the car? Car is driven less than 3,000 miles a year.
> 
> I looked into purchasing a refurbished unit through Auto ECMS. However the unit will need to be reprogrammed. I'm wondering if that has to be reprogrammed by a dealer or my mechanic. It's my understanding the Audi dealers programming is exclusive to them. Can anybody shed any light on this?


I suppose it is possible that you could have issues with binding but you would only really feel them while turning the vehicle - the rear wheels theoretically should not affect straight line driving but I could be wrong.

The units do not get "reprogrammed". They all have set programming from the factory and are all plug and play. Any controller from any year MKI TT will fit on any other MKI TT with no modifications. Anyone who tries to sell you on something like that is trying to steal your money.

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## B1-16V (Aug 5, 2002)

Just taking a stab in the dark here, but is it possible that this car has a couple issues going on with the Controller - 

1) MAYBE the controller is stuck in the on position (maybe from lack of use? Not sure if that's possible - Mine seemed to be stuck in the on position).

2) And IF the controller is stuck in the on position, could it be possible that only one clutch pack is working? Causing a pull?

This is all hard to understand with such low miles. 
But the fact that jsmBora1.8T is saying when the controller was unplugged the pull went away, 
(as long as the shop is being truthful and actually DID pull the plug to the controller) that is strong evidence it's a Haldex issue.

The fact is this - Haldex controller doesn't choose what side to put power to. It only turns on or turns off rotation from driveshaft to rear dif.


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