ABS, Trac Off, Brake, Service Traction System.
 

ABS, Trac Off, Brake, are all lit when starting car and "Service Traction System" lights when starting the car :-( ... I had this happen 1 other time when I did my Cold Air intake, the ground wire wasn't making contact from the PCM. https://cimg9.ibsrv.net/gimg/monteca...a5cc9540a1.jpg


Double checked that and NO... as others have done, I've searched and searched, and see wheel hub stuff; but for all to come on at the same time?!? scan codes aren't even telling me anything; 1040 Loss of Class 2 Communications with ABS (Pending) (Old) (History) (Current) (Immature)...

Lots of help that is! ABS and Traction Control haven't been activated in months... GRRRRRR off to the archives I go.

It's a long shot but check the wires coming from the front wheel bearings. Maybe someone else can give you more idea's. Good luck

Do the lights stay on after starting? I need to double check but I thought I recall the brake light always coming on when the car is first started then going away....maybe I'm mistaken. I would second that speed harness check.

Yes, my brake light would stay on all the time. Found the problem; see attached picture. The plastic clip that is supposed to keep the harness in place, no longer works as intended, with the clip "locked" you can still pull the plug out. My guess is that it worked it's way out, just enough to throw all the lights, unplug and re-plug and I'm good till I go over a bumpy road. Lucky for me, this is an easy fix :D (yes there is a first time for everything)... For others that are reading this thread with same lights, I found https://montecarloforum.com/forum/monte-carlo-repair-help-8/abs-traction-control-problem-13022/ a very helpful thread and I'll link back here in case others find that one..
https://cimg1.ibsrv.net/gimg/monteca...01af6e16bf.jpg

I'm glad you found the problem! And thanks for linking the other thread to help others!

Good find! I had a similar problem last week, when I read the codes it told me short/broken WSS sensor, all the wires looked good so I changed the hub out with a new Timken one and it works fine now. The old hub was shot, when I banged the hub out of the spindle, I got an open back with all of the grease and ball bearings exposed, and the back of the hub was stuck in the spindle. Got a chance to use my seal puller!
Dave