2004 XC90 T6 Traction Control Module

[SuperHerman]

A relative brought the 2004 XC90 T6 to the dealer for a "Skid" message. It was my old car - and now again part of my fleet.

Dealer stated that either or both the Traction Control Module or Brake Control Module are at issue. The computer cannot see them. When I ran the on-board diagnostic I received a "SET" reading - so as I understand it the system is not communicating to the modules.

Dealer stated that the Traction Control Module is first in the chain and if it doesn't get read then the rest in the chain will also show "SET". This is consistent with my understanding. I don't blame the dealer or Volvo - it is just how the system has to operate.

So the questions are:

1) What is the best way to remove the Traction Control Module on the 2004 XC90 T6 (and below years)?(newer models have it with the clock spring)

2) Will a used unit work or does it have to be married to the car and/or need a software update? (I have not found a definitive answer here but hints of same year, part number and option levels seem to float around - but no one saying I did it and it works). The like for like swap seems to work any many Volvo modules where the VIN/immobilizer is not attached in my experience.

A used Traction Control Module - like for like - can be had for $40 or less - Xemodex is $250 - dealer wants around $700. I wouldn't have such a hard time spending the money were I to know for sure I also don't need the BCM, which is $500 or so at Xemodex and over $1k at the dealer. In addition other demons may be hiding behind the first two codes - for example the Haldex pump may have issues which ruined the BCM - which ruined the Traction Control Module.

By the way - the car runs and operates fine. No limp mode - no pulsating brakes. Dealer stated only the DTS is inoperative.

[SuperHerman]

Here is an update to my first question:

For a 2003 and 2004 XC90 T6 (I believe the 2.5T is the same) to remove the Traction Control Module one proceeds like they are going to remove the CEM, but only so far as gaining access. Note: Later models have the unit integrated into the Clock Spring. The Traction Control Module is held in place by two little clips that once depressed allows the module to slide out. Then disconnect the green connector and the unit is out. The green connector wire is held in place by two plastic fingers that permit the cable to stay flush - it pushes out of these easy. 10-15 minutes.

I ordered a used Traction Control Module from allegedly a like year and model 2004 Volvo XC90 T6. For $35 I will take a chance, although if it doesn't work plug in play, I will not really now the cause. I will keep this updated for future users.

[FLXC90]

What is the actual message on the DIM? Anti-skid service required? I assume they ran real diagnostics? Most common cause for this message is a failed Yaw Rate sensor in the water under the passenger seat. (except for Mike!) Have you seen actual diagnosis?

[SuperHerman]

Unfortunately, I don't have the actual papers from the dealer.

I hooked it up to a Snap-On Solus Ultra and have the following codes:
1) 928C, ECU communication error;
2) 0109, Communication between control units communication problems with SAS, Internal Fault; and
3) 004B, Steering wheel angle sensor, Faulty Signal.

These are consistent with the built in DTCS computer data - which shows the relevant modules in "set" or "checking" status.

Yaw Rate sensor is doubtful as the car is and has been dry.

I believe the issue is related to a spill the car suffered, looks like a red smoothy or a great quantity of taco sauce from the residue that is all over the place. Current theory is it dripped down and ruined the clock spring. Following the path of the residue it appears to be a viable theory.

I bought a used clock spring, which should swap out without issue. I also bought a used SAS module, which will be a like for like swap. Here I will find if a like-for-like swap is possible. (Although I took out the SAS module, opened it up, and everything is clean and orderly with no signs of spills, cold joints, burned parts ... So I will first do only the clock spring and keep the original SAS module to limit the number of changed parts).

I noticed the steering wheel is not centered correctly, so I am going to have a friend check the alignment, align and/or replace suspension as needed, then remove the steering wheel and swap the clock spring. After this I will calibrate per and with VIDA.

Looking at the paper work I found a receipt showing the key tumbler and related electronics was changed out by the dealer recently. I am not sure if they removed the steering wheel to do this - hence the wheel being off center. But, if my spill theory is correct - the electronics of the key tumbler would have been bathed in the smoothy or taco sauce - leading to its failure. Likewise the offending liquid would have dripped right into the clock spring.

I will know more once I remove the steering wheel and inspect.

[SuperHerman]

Success! As I thought the toxic smoothy or taco sauce caused damage to various electrical components. I have attached some photos. I removed the airbag, steering wheel, clock spring, left and right stalks and steering wheel module.

Clock Spring showing the remnants of some spilled liquid. Seeing the mess I took more components off.

Clock Spring.jpg (265.56 KiB) Viewed 2511 times

Removing the clock springs I found the pins that plug into the Steering wheel module board were corroded.

clock spring pins.jpg (221.88 KiB) Viewed 2511 times

Looking at the Steering Wheel Module connector I knew I had an issue here also. I removed it and clean it up and added some dielectric grease to prevent further corrosion

Steering wheel module connector.jpg (154.06 KiB) Viewed 2511 times

I replaced the Clock Spring with a like for like used unit. I did not calibrate anything, I will once I get the alignment, but after driving the car about one block the anti-skid light turned off by itself. So the system is now fully functional and communicating.

In the end I did not replace the original steering wheel module I had purchased with the used unit so no need for the possibility of a software update.

I wonder how many failures are caused by spills that end up corroding the connectors. Although I was tempted to try and clean the original clock spring pins to see if the corrosion was the cause of the issues, having the used working unit on hand sent me down the easy path. It didn't make sense to put it back to together only to take it apart again. But, if one finds similar conditions and one has not bought a new unit - it would be worth a try.

I did some research on using dielectric grease and asked some knowledgeable engineers - they felt that due to the evident corrosion, it would be best to use it to prevent further degradation of any contact surfaces.