Ive got a curious one to fix today. ABS is not working correctly. Customer complaint that it brakes OK from speed but doesnt brake at low speed. I did duplicate it when I pulled it inside and the ABS went off just from a creeping speed brake apply.

I searched and didnt find anything on the forum,but you guys are usually sharp about odd problems.

-Pete

 

one of the wss signals is dropping out. the a/c volts signal is weaker the slower the vehicle speed and stronger as the reluctor wheel turns faster. so that is why it drops out at slow speed. the abs module sees the drop out and thinks that the wheel is locking up...and opens the dump valve.


check for codes, a loose wheel bearing, green or near broken wiring at the sensors.
if that is all good. record and plot the wss data with a scan tool. the plotted line graph with show which sensor is dropping out.

 

Thanks tech2. I was able to isolate that the L rear was dropping out about 10 mph. I didnt find anything other than a bit of grease in the reluctor cavity so I replaced the sensor. Test drive is coming soon to confirm its fixed.

-Pete

 

i'm betting its fixed.

 

pretty common issue on gms