Q: "TRAC OFF" light came on after diagnostic test for check engine light

asked by on November 24, 2016

My check engine light came on a few days ago so I took it in for a check and they determined my knock sensor was bad. I had more detailed diagnostic testing done and when I picked it up, my "TRAC OFF" light was illuminated! I returned to the shop to ask if they may not have hooked something back up and was told that additional lights will probably start coming on until the knock sensor is fixed. I questioned the relation of the knock sensor to the traction control and he said it was just the way the electrical circuit works. What are your thoughts on this? I feel like I'm not being given correct information just so they can get the $800+ to fix.

My car has 201000 miles.
My car has an automatic transmission.

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Hello. In most cases the vehicle’s traction control system is on a completely separate circuit then that of the engine knock sensor. Therefore most knock sensor faults or issues should have little to no effect on the operation of the traction control system. The traction control system operates using wheel speed sensors installed in the vehicle’s hubs, and it is usually an issue with these, or with the computer, that sets off the light. Just the same as a check engine light, a compatible scan tool can be used to determine what is causing the traction control light to come on. If the light came on after that particular shop worked on your vehicle then they should be able to help you determine what the problem is, as the issue was not there when you gave them the vehicle. If they are unable or unwilling, I would recommend having a professional technician, such as one from YourMechanic, come to your location to diagnose the cause of the illuminated traction control light.

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