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Discussion Starter · #1 ·
Hello all.
Last year I noticed my mk4 r32 turned into fwd. I ran output tests via vcds and the precharge pump was not turning on.
Fuse 31 checked, its okay.
I checked the wiring from the 8-pin connector for the Haldex control module. Everything was fine there so I replaced the precharge pump (I had a spare one). Still no awd and the old pump turned out to be fine (it runs with straight 12v).

Cleared all the fault codes and this one kept on coming back:
01155 - clutch 04-10 - mechanical malfunction - intermittent

Since then I bought a spare control module and installed it a couple of days ago. Still no awd and the precharge pump won't turn.
So, wiring is okay, pump is working and control module should be working. I did check the function of the brake light switch and parking brake switch via vcds again and I get the correct voltage to the 8 pin connector.
Now, after driving a few days, I can't get any fault codes back.

Whats next? I want to believe I dont have 2 faulty control modules here. Could it be a problem with abs or ecu? Or the data bus wiring is faulty?
 

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Discussion Starter · #3 ·
Clutches inside can be damaged, forcing the controller OR the pump to not turn on. It is the last possibility, unfortunately
Really? I thought the controller tells the pump to turn on/off when needed and then controls the oil flow/pressure in the clutch. So the pump would turn on without oil or even independent from the actual clutch.

I don't believe there is a problem in the clutch pack as I change the oil very frequently and the oil and filter comes out clean every time.
 

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You can easily get two faulty modules - they leak water in and die.

The precharge pump not running means there is no base pressure. The precharge pump pumps a fixed speed and the accumulator actually regulates a fixed pressure. The difference in speed between the input and output is what provides the lockup pressure ABOVE what the pump supplies. Then the regulator valve is adjusted to reduce working pressure if required, to allow some slip.

You should have an output test in VCDS to run the precharge pump (possibly the only test in the haldex unit?), otherwise it will run whenever the engine is running above a certain speed (4 or 500 rpm?).

It that test works, then the haldex ECU has control of the pump, but isn't turning it on. If it doesn't, something down there may have failed.

If the Haldax CAN turn on the pump, maybe look at the required signals and other modules for faults.
 

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Discussion Starter · #5 ·
You can easily get two faulty modules - they leak water in and die.
Yes, that is possible. The controller was told to be from a working unit, but you never know these ebay scammers.
However, I took the old controller apart. There was no visual damage and the wiring loom was alright. The failed controllers I've had seen have usually oil/water leaked into electronics side and thats what fries them. But yes, anything is possible.

You should have an output test in VCDS to run the precharge pump (possibly the only test in the haldex unit?), otherwise it will run whenever the engine is running above a certain speed (4 or 500 rpm?).

It that test works, then the haldex ECU has control of the pump, but isn't turning it on. If it doesn't, something down there may have failed.

If the Haldax CAN turn on the pump, maybe look at the required signals and other modules for faults.
Yes, I did run the output tests. Pump does not run. None of my tested pumps with any of the two controllers.

Do you happen to know, would the output test in VCDS run the precharge pump if there was a problem in the data bus wiring?
 

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If there is a break in the wires, you should loose all comms, unless it can do it over k-line, but I don't think it does. I know the MK5 better - it just has the can bus comms.

If you can access the output test though, you're communicating with the unit - there should be a faulty comms code, if it can't send/receive data.

Have you applied 12v to the pump under load (installed with oil?) or have you check for power at the motor plug while activating the test? Just to confirm if the controller is sending power or not, 100%?

Have you got fault codes in any other modules?

The brakes being on, or the handbrake on, I beleive will stop the 4WD engaging... but I think the pump should still run, at least when the output test is run.
 

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Really? I thought the controller tells the pump to turn on/off when needed and then controls the oil flow/pressure in the clutch. So the pump would turn on without oil or even independent from the actual clutch.

I don't believe there is a problem in the clutch pack as I change the oil very frequently and the oil and filter comes out clean every time.
Pump is always turned on. Controller tells to apply pressure or not to an actuator.

On your problem, as the pump turn on with a direct 12V and not in your car, and you have a good fuse, good wiring (because your checked all the pins and you said it has the good voltage), and I cannot think of 2 faulty module too because you can connect your computer to them, I would say that there is a mechanical malfunction in your haldex, as the DTC shows.

Even if you make the regular fluid change and clean the pump, you cannot avoid a problem with the clutches.

At your point, I would say that you do not have any other options than :

1) Test your hardware on a working car (pump & controller but not easy to find a car....)
2) Check another haldex or open it.

Di you get "grey" stuff when changing your fluid?
Was the oil burned?
 

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Discussion Starter · #8 ·
Have you applied 12v to the pump under load (installed with oil?) or have you check for power at the motor plug while activating the test? Just to confirm if the controller is sending power or not, 100%?
I haven't. That will be next thing to do, but thats kinda pita as im working on jack stands and the plug is not very accessible.

Have you got fault codes in any other modules?
At the moment there is no fault codes with the new module installed.
 

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Discussion Starter · #9 ·
Pump is always turned on. Controller tells to apply pressure or not to an actuator.
Well yes, but the power still goes through the module.

Di you get "grey" stuff when changing your fluid?
Was the oil burned?
As far as I remember, yhe fluids allways been pretty clear. I happened to have the old filter from my last oil change before the haldex was still working. Nothing but some minor dirt in there.
 

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Discussion Starter · #10 ·
So, after driving 1000 kms or so and launching several times, there is no fault codes. When running the output tests, I can hear a faint high pitched sound coming from the haldex module, so there is some life in it. The old module did not do that.
The pre charge pump still does not run.
 

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Discussion Starter · #11 · (Edited)
I plugged my other working pump on the new controller thats on the car right now and ran the output tests. The pump runs so the controller is working.
Then I run wires from a spare battery to the pump thats in the car. No cigar. It clicks and is trying to turn but thats it.

So either there is hydraulic pressure thats too much for the pump and is keeping it from turning or the pump is weak or jammed somehow.

Im going to get one more tube of that precious oil and drain the system and change the filter, switch the pumps and test everything one more time. Then I think it's time to source a new clutch pack.
 

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Discussion Starter · #12 ·
Well that was an interesting one. I took the pump out and it was stuck somehow. Replaced pump, oil and filter and everything is working now.

The fun part is that I couldnt find anyhing wrong with the pump that was stuck. I looked inside - nothing there and put it back together. Tested it and now it turns and pumps oil like it should.
 
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