I have codes [(03) 01324 CM for AWD no comm] and [(22) 01312 Powertrain Data Bus faulty or intermittent].

I looked at ABS Control Module Measuring Block 125. The ABS is talking to the ECM and the Steering angle sensor, but not the Haldex.

The DTC table only says to check the wires for these codes. So I shot the CAN wires down to the Haldex and they check good. My diagnosis is that the Haldex CM is faulty. I would have thought I would get 65535 if it was bad.

I did the Haldex check in the FAQ and everything seems okay, All four wheels are spinning. (rears spin up good in the rain)

So I looked at all the options. Dealer, Wrecking Yard, Ebay, HPA. HPA seems like the best choice. The part is new and is performance based. The wrecking yard or Ebay parts can fail in a short time with no recourse.

So after all that I figured I would get an expert opinion from here.

Did I miss anything?

Can the Haldex be locked up causing the wheels to spin, but not unlock causing the comm problem?

This would be my first Mod, but wouldn't be a cheap mistake if I am wrong.

Thanks for the help.

 

The part that calls for applying the parking brake. Also check your Brake light switch. A failure there will turn off the Haldex. Did you do the on ground tests? A CM failure usually results in no activity back there...

 

Your right. I will do the check again. I did not check the brake signals at the CM conector, no helper.

Are you saying if the CM was failed my rear wheels would not spin? (usually)

 

On a side note I found World Impex through your site. I am trying to get the MAF dealt with.

Mine is a 06A 906 461 E. They have a 06A 906 461 D. Are these interchangeable?

ECS Tunig just throws up a rebuilt or a new, no OEM P/Ns.

 

yep....Haldex failure usually equals front wheel drive "only"......

 

Don't worry about those. You need a 461EX (Remanufactured)for an AMU motor. There's no way a Maf element can be "remanufactured" as they are pretty complex. Just the tubes are recycled, and honestly every one I've bought that was supposedly a reman one has been like new. You don't need the tube anyway

 

There is still some engagement in the air. You're dealing with a 7 (I think) plate clutch so there will always be enough drag to turn the rear wheels even when disengaged. Follow all the steps..


Function-test of the Haldex coupling.

- Rollout in circle

Aim: Check the function of the coupling and the response on the car. Is to be done on level ground.

1. Drive in circle with minimum turning radius at a speed of about 10 km/h.
Disengage the clutch and close the throttle.
Let the car roll to full stop.

2. Drive in circle with minimum turning radius at same speed as in case 1.
Disengage the clutch and run up the engine to 3000 - 4000 rpm.
Let the car roll to full stop.

* If the coupling is working the car will stop in about half the distance in case 2 compared with case 1.

* If there is no difference in the two cases there is a malfunction of the coupling. The problem could be caused by the coupling or by missing signals from the car. A further inspection has to be done to be able to determine the cause of the malfunction.

* If a noise from the HLSC is noticed when turning or driving in circles the oil in the coupling is damaged. The damage can be caused by overheating or by water in the oil.


- AWD test on car lift. (all wheels free to turn.)

Aim: Check the function and the control of the coupling.

1. Pull the handbrake.
Disengage the clutch.
Start the engine.
Put the gearbox in 2:nd gear.
Let the engine idle.
Engage the clutch.

* Engine is supposed to stop when the clutch is engaged. (HLSC controlled as in handbrake start.) If engine do not stop, disengage the hand brake immediately. Otherwise there is a risk of seriously damage on the HLSC.

2. Disengage the handbrake.
Disengage the clutch and start the engine
Put the gearbox in 2:nd gear.
Let the engine idle.
Engage the clutch. At least one front wheel and one rear wheel is supposed to turn.
Pull the handbrake for 2 seconds.

* Front wheel is supposed to turn while the rear wheels are supposed to stop when the brake is pulled. Engine is supposed to run all the time. (HLSC controlled as in handbrake turn.) Don't exceed the 2 seconds or repeat the test for more than 5 times during a 5-minute period. Otherwise there is a risk of seriously damage on the HLSC.

 

my wheels were binding on tight turning circles. Haldex was not compensating for difference in turning radius between inside/outside wheels. Dealer replaced under warranty and problem went away.

 

Sorry for the delayed reply. I was tied up yesterday getting the A8 back from the shop on transmission warranty work. They finallly got it right, new torque converter and new pressure pump. The only problem was when they reconnected the battery the sunroof opened and jammed in the full open position. They were flustered and I was fuming. How dare thier tech go joyriding in my car and break my sunroof. That sunroof didn't open on it's own! (or did it?) An open sunroof in February in the NW is not a good thing. I told them I did not want them to fix it, I would take care of it. AudiWorld to the rescue. I found several threads where the sunroof does this when the battery is reconnected. It was a simple fix to pull the motor, crank it closed, and zero the motor.(has a little crank under the sunroof switch cover, those freakin' Germans are awesome!) Anyway the car performs beautifully.

Back to the TT. I didn't get the driving test done, but did do the power, ground, brake/ebrake switch checks, they are good.

I can't do the driving test because I need to change a wheel bearing. I believe the car was driven through some water and then sat at the dealer. If water gets into a wheel bearing and then sets, it pits and then starts to rumble.

So I ordered a Haldex Service Kit and a Haldex CM. HPA is backordered so they are sending me a loaner stock unit on Friday. This will certainly verify the CAN Comm problem.

I ordred front ball joints and tie rods as well.

Since I am in there and using a hydraulic press from work, what are the odds of pulling off a DEFCON 3 install?

This would require Modshack to ship overnight and World Impex to do the same. Possible?

Anyway MAF is probably going to be new. ECS is having trouble (snow). I have to get everything done this weekend. Need the car.

Also I had to get a headlight switch the "not so bright aftermarket alarm installer" jacked that part too. I came out to go to work in the morning and the license plate light was on. Went to pull the switch (per Bentley Manual) and it fell apart. I'm pretty sure the alarm installer didn't remove it properly and then just stuffed it in the hole.

I will try to email Modshack about thye possibility of DEFCON 3. If I am in there...why not!

I know it will all be worth it when the sun is shining on my partially bald head and I am zipping down the motorway in my dreamcar. (Pre R8).

Thanks for the help.

Will post all results.

 

YGM RE: Defcons..