MID 136 SID 66 FMI 7 traction control light on HELP!!

Have they checked the tone rings at the wheels for missing or damaged teeth?

 

I have gathered that you have a Volvo from the forum that it's posted in, but since year, model and what ABS is a secret, I don't know what manual to look in to help.

 

Ah Bendix. Well, I get conflicting info. The manual in Bendix Acom says that SID 66 is the trailer PWM, which must be a misprint because there is no FMI 7. So it just doesn't make much sense and probably why the dealership is confused as well.

I have another generic code look up program that says that SID 66 means, pneumatic back-up pressure control axle 3. Axle 3 is a little confusing also, unless you have a 6 sensor system on you tractor, which is possible. It is a generic program, so it's not perfect. I've seen pneumatic back-up pressure control in the past and it was related to the traction control system, so that makes sense. FMI 7 means a mechanical system is not responding correctly or out of adjustment. It is most common in the traction control, when a wheel begins to spin, it applies brake pressure to that wheel, if there is no change in wheel speed, it thinks that the brakes are not working correctly.

It could be a traction control valve that is OK electrically, but not mechanically. It could also be mechanical in the brakes themselves. The first thing that I would do is to verify the configuration in the ABS ECU matches what is actually on the truck. That could be a tough one to pin point. If it happens more in the rain, I'd be looking for corrosion or chaffed wires.

I had one drive me nuts for a while and Bendix was no help. The engine would derate and trac light flashed. No DTC's, but in events, it showed that the Mud/Snow was coming on and off. Bendix said that the driver must be hitting the Off Road button on the dash. The problem ended up being rubbed through wires under the dash. It was the wires going to the Off Road switch.

 

It has been mentioned numerous times on the site and I'll help you out, there is a sensor in the steering wheel that's out of adjustment, you can clean it yourself or you have to take it to the dealership to get it reprogram.
Some truck have sensors on all four wheels in the rear. The wires for the sensor in question shavft over time, you will be place all four or you will chaseing this code for a while.

 

Here is the link :
http://www.thetruckersreport.com/truckingindustryforum/volvo-forum/155614-tsc-light-is-on.html
I hope this helps your problem