Traction control light and comm issues mk1 TT

[Zak99b5]

I bought my TT a couple weeks ago. I get an esp/traction control light sometimes, and sometimes not (about 50/50 I'd say).

Sometimes when I turn the key on, I hear the pump run for the haldex. Not always. Most times I hear the pump run, I do t get a light. But not always.

Sometimes I hear a knocking kinda sound from the rear end, car not moving. I think it's the pump teyingstart for a slight moment but obviously not running. I think I've only heard this with the traction control light on, but not 100% sure.

I don't know if awd is working when the light is on, but I suspect it's not.

The other day I unplugged the connection to the haldex that's by the muffler. Pins looked ok. Plugged it back in. Didn't get the traction control light for about 6 or so starts in a row after that, but of course now it's back on.

main codes I'm seeing in the haldex controller are 01312, 01314, 01316.

code I get in the abs is 01324.

all communications codes. Also, seems like no communication with the cluster--is the gateway in there?

Autoscan:

Wednesday,21,May,2025,18:30:28:31948
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 25.3.1.1 (x64)
Data version: 20250415 DS365.0
www.Ross-Tech.com


VIN: TRUWX28N611033409   License Plate: MK1 TT
Mileage: 155968   Repair Order: autoscan



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Chassis Type: 8N (8N - Audi TT (1999 > 2007))
Scan: 01 02 03 08 15 17 22 35 37 45 55 56 76 77
 
VIN: TRUWX28N611033409  
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Address 01: Engine        Labels: 06A-906-032-AWP.lbl
   Part No: 8N0 906 018 L
   Component: 1.8L R4/5VT     G   0003 
   Coding: 07700
   Shop #: WSC 01236 
   VCID: 3A7537782623554BC4-515A
   TRUWX28N611033409     AUZ5Z0A1120092

No fault code found.
Readiness: 0000 0000

-------------------------------------------------------------------------------
Address 03: ABS Brakes        Labels: 8N0-907-379-MK20-E.clb
   Part No: 8N0 907 379 E
   Component: ESP     20    CAN  V005  
   Coding: 18446
   Shop #: WSC 01236 
   VCID: 3E7D3B683A0B796BF8-4B18

1 Fault Found:
01324 - Control Module for All Wheel Drive (J492)
            49-00 - No Communications

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Address 08: Auto HVAC        Labels: 8N0-820-043.lbl
   Part No: 8N0 820 043 A
   Component: TT-KLIMAVOLLAUTOMAT D03 
   Coding: 00140
   Shop #: WSC 01236 
   VCID: 2851FD30C88FD7DBA2-258C

No fault code found.

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Address 15: Airbags        Labels: 8N8-909-601.lbl
   Part No: 8N8 909 601
   Component: Airbag Front+Seite 1008 
   Coding: 10103
   Shop #: WSC 01236 
   VCID: 77F3EE4C55B18823FB-515A

2 Faults Found:
65535 - Internal Control Module Memory Error
            00-10 - - - Intermittent
00588 - Airbag Igniter; Driver Side (N95)
            68-10 - Cylinder 1 - Intermittent

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Address 17: Instruments        Labels: 8Nx-920-xxx-17.lbl
   Part No: 8N1 920 930 J
   Component: KOMBI+WEGFAHRS. M73 D56 
   Coding: 07244
   Shop #: WSC 00050 
   VCID: 38712D70182F475B32-FFFE
   TRUWX28N611033409     AUZ5Z0A1120092


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Address 22: AWD        Labels: 02D-900-554.lbl
   Part No: 02D 900 554 B
   Component: HALDEX LSC  ECC     0006 
   VCID: 1F43E6EC9DC11063D3-4B18

3 Faults Found:
01312 - Powertrain Data Bus
            37-00 - Faulty
01316 - ABS Control Module
            49-10 - No Communications - Intermittent
01314 - Engine Control Module
            49-10 - No Communications - Intermittent

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Address 35: Centr. Locks        Labels:. 8Nx-962-267.clb
   Part No: 8N8 962 267 A
   Component: Central Lock/Alarm  D05 
   Coding: 15884
   Shop #: WSC 00050 
   VCID: 3F83466C3D017063F3-4F1E

2 Faults Found:
01370 - Alarm triggered by Interior Monitoring
            35-00 - -
00957 - Key 3
            09-10 - Adaptation Limit Surpassed - Intermittent

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Address 45: Inter. Monitor        Labels: 8E0-951-177.lbl
   Part No: 8N8 951 177
   Component: Innenraumueberw.    D09 
   Coding: 00001
   Shop #: WSC 00000 
   VCID: 7CF9F1606C97AB7B96-51B2

2 Faults Found:
01463 - Alarm triggered by Sensor for anti-theft alarm System
            35-00 - -
01462 - Anti-theft alarm ultra sonic Sensor (G209)
            53-10 - Supply Voltage Too Low - Intermittent

-------------------------------------------------------------------------------
Address 55: Headlight Range        Labels: 4B0-907-357-AUT.lbl
   Part No: 4B0 907 357
   Component: LEUCHTWEITEREGLER  D004 
   Coding: 00010
   Shop #: WSC 01236 
   VCID: 65CFB404FF1D0AB359-51D0

1 Fault Found:
01539 - Headlights Not Adjusted
            35-00 - -

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Address 56: Radio        Labels: 8D0-035-1xx-56.lbl
   Part No: 8N0 035 186 A
   Component:  Radio              D05 
   VCID: 2E5D0B28EA6B89EB68-4B18
   Note: Excessive Comm Errors


End-------------------------(Elapsed Time: 04:56)--------------------------
------------------------------11 Faults Found------------------------------

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Address 03: DTCs cleared
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Address 22: DTCs cleared

 

[Zak99b5]

Update: I can connect to 17 instruments.

I cannot communicate with 19 CAN Gateway. But I'm not sure my car actually has that.

 

[Uwe]

I cannot communicate with 19 CAN Gateway. But I'm not sure my car actually has that.

An Mk.1 TT does not have 19-CAN Gateway.

Based on your fault codes, it looks like a dodgy connection on the CAN bus in the general vicinity of the Haldex.

-Uwe-

 

[Zak99b5]

That's what I thought. There's no address 19 in the Autoscan, either.

 

[Dr Sheldon]

You need to do work here !

On that scan ABS is bitching about No Comms with AWD ?

Yet AWD is communicating and reporting fault codes for No Comms with Engine & ABS yet Engine is not reporting a loss of Comms with AWD.


I would suspect one of those modules is corrupt - Either ABS or Haldex.

Might be an idea to remove one at a time ?

 

[Dr Sheldon]

Also, seems like no communication with the cluster

I dont see any evidence to support that guess !

 

[Zak99b5]

You need to do work here !

On that scan ABS is bitching about No Comms with AWD ?

Yet AWD is communicating and reporting fault codes for No Comms with Engine & ABS yet Engine is not reporting a loss of Comms with AWD.


I would suspect one of those modules is corrupt - Either ABS or Haldex.

Might be an idea to remove one at a time ?

Ok, so let's say I unplug the haldex. What do I look for to be different if it's the haldex that's bad? Same question if I unplug the abs controller?

I'm going to unplug both the abs & haldex so spray some electronics cleaner in the plugs to see if that makes a difference.

 

[Dr Sheldon]

Ok, so let's say I unplug the haldex. What do I look for to be different if it's the haldex that's bad? Same question if I unplug the abs controller?

I would be looking to lose

3 Faults Found: 01312 - Powertrain Data Bus 37-00 - Faulty

 

[Zak99b5]

Pulled out the airbox to clean up the abs connector, but there wasn't enough clearance above it (under the plastic wiring channel) to remove it completely. So I just worked it on & off a few times just on the off chance that will make a better connection.

 

[Zak99b5]

I would be looking to lose

Ok good to know. I was thinking of the other codes, which wouldn't clear with the module unplugged.

I'll do that & report back.

 

[Zak99b5]

Raining out so I didn't feel like crawling under the car but I did check out channel 125 on the engine, abs, and awd.

Engine was totally happy (no surprise, no codes)
Blank, abs 1, instruments 1, blank

Abs was less so
Engine 1, SAS 1, awd 0, blank

Awd even more upset
Engine and abs flickering between 0 & 1.

This is making me think the abs is ok (and, indeed, I have no abs light nor any codes that deal with that system itself).

So I will focus my efforts on the haldex cm. I'll clean out & reseat the connector plug, but I see there's a second (2 wire?) connector that's on the cm itself in addition to the main one by the muffler/behind the diff. What's that for?

 

[Zak99b5]

According to my reading of the Bentley diagrams, the two-pin connector is for the haldex pump.

Wires 7 & 8 are for the comms in the main connector. Going to look hard at those.

 

[Zak99b5]

Cleaned the 8-pin connector real well after doing the rear suspension.

Traction control light popped on a couple yards down the road.

Looking more & more like the haldex is bad.

 

[Zak99b5]

Can I test the can low & hi signals at the car side of thr plug for the haldex with a dmm on pins 7 & 8 (can wires)? Am I looking for voltage there, or would I need an oscilloscope? Or maybe just test continuity, but I don't know where the other ends of those wires live.

 

[PetrolDave]

I don't know where the other ends of those wires live.

I think a wiring diagram (that's a link) could be useful.

 

[Dr Sheldon]

Can I test the can low & hi signals at the car side of thr plug for the haldex with a dmm on pins 7 & 8 (can wires)?

Can is bi directional so you can look for it anywhere on the network.

Powertrain CAN on your car I believe runs at 500kb/s so an oscilloscope would be ideal.


Moving on !! As long there is no short or physical corruption and the modules are communicating with VCDS then I doubt very much that the integrity of the Can Signals will be at fault - Worth a look though !!

I would be more inclined to think tis is a case of jumbled messages which is more a module fault.

Again some intensive and extensive testing is in order.


And is a CAN fault such as this would be enough to fool most / the majority of dealer techs - is it a DIY thing ??

 

[Zak99b5]

Ok so I did some testing of the car side harness.

With modules asleep, I got 60 ohms across can hi/lo, which is expected.

With ignition on, I got 2.6v/2.3v from can hi/lo respectively, again as expected.

I tried ohming out the hi/lo going to the haldex controller, but I wasn't able to with the awkward angle under the car and no third hand to hold both dmm probes and the plug plus a fourth to hold the dmm. I think I did manage to get on the pins and saw OL, but totally not certain. Plus I don't know if there's a spec for that anyway.

Really wish I had access to a spare known-good haldex controller to plug in as a test.

Also, when I was reconnecting the plug, it wouldn't lock together. Even with forcing the plugs together with pliers. So I zip tied it together using the bracket it mounts on.

Also, I noted the ground strap to the rear diff didn't look great (green wires at the ends), but when I did the voltage test I used the screw holes for the mounting bracket as my ground so I guess it's ok.

I do appreciate the feedback here.

 

[Zak99b5]

I think a wiring diagram (that's a link) could be useful.

I do have the Bentley for the car so have access to wiring diagrams, which I've been scouring.

 

[Zak99b5]

The plot thickens.

I hooked up vagcom to try the output tests on the awd.

They ran through, but I didn't hear the pump run. But the car door was open so I wanted to try it again with door closed.

Had to close the controller & open it again because it only said "test completed. So I ran it again, and again I heard nothing.

Thought I'd try once more, but now vagcom cannot communicate with the haldex. Other modules connected fine (engine and abs).

Really starting to think the haldex controller is bad now.

 

[Dr Sheldon]

Thought I'd try once more, but now vagcom cannot communicate with the haldex. Other modules connected fine (engine and abs).

Really starting to think the haldex controller is bad now.

First check that you still have power and ground to it !