Abs and Traction Control light every now and then

[NBv8S4]

quick question, every now and then my abs and the traction control light will come on on the dash. it will go away when the car is restarted and it doesnt happen every drive. usually occurs when im downshifting and braking at the same time. any idea what could be causing this? car drives fine even when these come on? im new to the s4 world and was just curious

[TypeRx]

I have some personal experience with this although I am sure there are multiple potential causes. Take off your front wheels and look to see if the wiring that runs in a similar path as your brake lines is okay. I think i is the vehicle speed sensor or something similar. The wiring connects near the axle (behind the brake rotor) and goes all the way to the rear (towards the rear of the car) fenderwell and is secured by a unique grommet. My grommet somehow got messed up allowing the wiring to have extra slack and rub against suspension components. I was getting some intermittent episodes of ABS and TC lights due to minor shorting of this.

My symptoms were similar...the ABS and TC light issue was triggered by heavy load or turning (I was at the track when it started happening).

[NBv8S4]

i will be doing the control arms next weekend so i will be sure to check that out while its on the lift. thanks for the help i appreciate it

[WolfS4]

Would be best to get the code scanned to find out exactly. Even when you turn the car off and back on and it goes away the code should still be stored. Mine just started randomly doing the same, and it appears to be due to a sticky brake light switch that's exacerbated by colder weather. Could totally be a wheel speed sensor too, and scanning would tell you which one.

[B6JoeS4]

Find someone with Vagcom and scan for codes. There will likely be a stored fault code.

ABS fault will cause the traction control to fault as well. But you can have an issue with traction control without also causing a fault in the ABS system.

[jhmotard]

If this an intermittent issue that happens when there is water involved, ie rain, carwash, etc. then you should look for water in a connector. But if this happens any random time then you may have a harness that has been chaffed through or a wowed out terminal. The code will tell you what to look for. A multimeter can be your best friend!!