I was driving down the highway yesterday and the traction control message came on. Going about 70 mph and in a straight line. The car slowed down. Definite power loss! My first thought was the car is insane.Which is usually the case. My second thought was the steering wheel position sensor was off alignment. Hence, the car would think it's turning at 70 mph and correcting. I took the car and had the front end aligned. The steering wheel was indeed off. I thought my issues were solved but the car disagreed. It did the same thing today. I had the EBCM rebuilt about 2 years and 4k miles ago. At that time it had the dreaded code we won't discuss. My next thought was the steering wheel position sensor was failing. I checked the codes and the only remotely related code was the right front tire pressure sensor. It was a history code and from about a week ago when the sensor forgot how to send signals. I am sure it's batteries are about to go, but can't find any relation to the larger issue. Why is my traction control coming on at 70 mph in a straight line on a dry road?

 

Have you changed tire size recently?

 

No. Same sizes for 2 years now.

 

EBCM failure

http://www.absfixer.com/

 

They re-built it two years ago. It doesn't throw an error code or say have serviced. Suppose I can ask ABS fixer his thoughts.

 

A clearer description would help.

Traction Control and Active Handling are two very different things.

When this occured, did the DIC say "traction sys active", or did it say "active handling"?

 

Valid point! "traction sys active" was on the DIC. If I push the button on the center console and shut off traction/handling, no more message. But it is the traction control. The button is not quite the fix I would like but a temporary solution.

 

It sure sounds like your Steering Wheel Poition Sensor is going out. It happened to me. Do you have a P1287 DIC code?. Rolling up to a stop I would get something like "Traction Sys active and TC disengaged". When the SWPS stops sending (or sends incorrect) voltage to the ECBM, the vehicle can assume that you are in a yaw condition. The ECBM will apply brakes to either the RF or LF wheel to correct for the perceived yaw.

This meant when I was driving down the freeway at 60 all of a sudden the car was yanked in to the lane to the right. Thankfully, No one was in that lane.

 

I agree a code would be nice! A big no on the P1287. Here are the only codes in it:
AO-LDCM U1064 H (U1064 Loss of Communications with DCM (No State of Health Message)
AC SCM B2606 H (B2606 Seat Rear Vert. Position Sensor Failure)
BO RFA C2105 (C2105 Right Front TPM Sensor Malfunction -TPM)

 

(post removed since the OP's reportted error message keeps changing).

 

So, in trying to be proactive, what is involved in the SWPS? Cost for the part? Effort to change? Might just be worth taking a guess at the issue and changing it.

 

I had the dealership replace mine. I didn't want to mess with the airbag stuff. The SWPS part is ~$80. The dealer charged me ~$250 to install. Some on this fourm have done it themselves. I also think someone actually did a write-up on the procedure. Hope that helps.

 

Any fresh ideas other than wait for it to throw a code and drive off the road?

 

I've been fighting the same unintended one front wheel braking for over a year. Every time I think I have it corrected, it will happen again. I feel that it is a poor design because it will active one brake when there is a malfunction before it turns off the active handling system. Doesn't seem right to me. I have gotten so disgusted that I installed an aftermarket module that keeps the active handling disengaged even when shutting the vehicle off and restarting. This because of brain fade on my part and I forget to turn the darn system off every time. This I can live with till I finally get this thing repaired. I haven't given up, just regrouping for another assault!!!! Good luck!!!

 

Mine still does it regularly. Now I find that it has a thing for 70 mph. It won't trigger the handling system until right around 70 mph. If the traction system is turned off, I don't get the issue. It still won't give me a code. I will probably try changing the SWPS with hopes that is it. All roads seem to lead there. Right now the double DIN conversion looks like more fun so that is my project for now. Probably not the big priority, but at least I know it will work. Please let me know if you run across any answers first!

 

I made it happen more to get a better feel for it. The car is not pulling leading me away from the SWPS. It only comes on during acceleration and only on the highway at about 70 mph. If I let off the accelerator, no more "traction sys" message. Push the accelerator and it comes on again. What tells the car that the rear tires are slipping? There must be a sensor failing back there. The tires are planted solid and not slipping in this case.

 

You sort of have to think this through. Don't confuse the different ways the ABS system works and reports failures. Active handling and traction control are two different functions of the ABS. Sometimes they work together and sometimes they don't. It all depends on the situation. Somebody who has one wheel braking and then getting a Service AH message has a totally different issue than you do.

As long as the DIC reads Traction Active you will not get a code. The system thinks it is OK. If you had a code you would get a Service Traction message instead. Since it is activating traction control the system is seeing a higher frequency signal from one or both rear wheel speed sensors. It could also activate if it saw a lower frequency for the fronts. Historically, when the system activates in the 70 mph range that usually means there is a tire size problem. Even though you haven't changed tires for a couple of years what size tires are you running and how worn are the rear tires?

If the rear tire size (not wheel size) is more than a half inch greater in diameter than the fronts you should be OK in that respect.

Check the wheel bearings. If you have a loose bearing that could cause alternating wheel speed frequencies which could trigger the TC.

There is a dead band programmed into the TC function. At lower speeds it will allow the wheels to spin a certain amount but as speed increases and the system needs to react faster the dead band is reduced. Differences in wheel speeds that are acceptable at lower speeds become unacceptable at higher speeds.

Think of it as a two dimensional plot with wheel speed difference on the Y axis and car speed on the X axis. As car speed increases the acceptable wheel speed difference asympotically approaches the X axis.

The SWPS may not be the problem. If it was you would probably get some unwanted AH activations before you got a TC activation.

Bill

 

Disregard my above reply, since the OP apparently changed which message he actually saw.

When asked to clarify the first time, he said "Active Handling", and that's what my response was based on. Now, he changed it to Traction system. SWPS would have nothing to do with that.

 

Looks like tire size is the answer! The fronts are 245/45-17 and the backs are 295/35-18. If my calculations are correct, my front is 25.7" tall and the backs are 26.1" tall. That's a .4" difference is all were new. Looks like the backs wore a little and make the traction control kick on. Need to go with a taller rear tire to get rid of it or ignore it until I am ready. Thanks!

 

I'm not meaning to make you look bad. Judging by the "post removed since the OP's reportted error message keeps changing" response, that is how you feel. The active handling message came on the first time. Having the car aligned got the steering wheel straight and fixed that. When the code came on I thought it was the same. That was my error. I don't "keep changing" the message, just corrected it to get the facts out there. I apologize if my error offended you. I appreciate the input from you and the others! I hope as my knowledge of C5's grows I can pass the favor on to others.