1tufam

I have been reading many threads about the issue of ABS INOP and TCS off and switch does not do anything. There is not a good answer to this question. The solutions are all over the place. I have discovered a common issue. When we are spinning the rear wheels and not moving the the front wheels it seems to cause the lights to come on. Cases such as running the car on jack stands, dyno testing, using a line lock at the track, etc., have prompted many to post that their lights have turned on.

Is there a reason for this? I have this problem with a 99 TA M6 that I was running in 6th gear on the lift trying to find a bad gear noise in the rear end (the salvage yard axle is worn out and howling). The car had never lit up these lights before. Does the computer have an issue with 90+ mph on the rear axle and nada on the front? Can the computer/ABS learn its way out of this problem? Some have posted that after a period of time the lights will go out and the systems will work again. Can you disconnect the battery and let the system start over? Does the code need to be cleared? Anyone in Kansas City have the cool guy scanner for this laying around?

Just hoping to solve my problem and many others.


Thanks for the help in advance.

trans_am7935

iTrader: (15)

the ABS gets it's reading from the 4 sensors on each corner (or from the rear dif ring gear if no Traction control is equipped) of the car and determines that that all 4 wheels are rotating in the same direction at the same speed. when the computer reads that all 4 wheels are not turning the same (ie burnouts, dyno) and braking is not being applied, then the ABS module will disable itself, TCS along with it, as the ABS needs to be operational for the TCS option to function.

the lights should go off shortly after the sensors read that all 4 tires are spinning the same speed. if your lights remain on, or are on all the time then it can be a few things

-bad/dirty wheel speed/ring gear sensor
-bad ABS module
-dirty/corroded with brake dust connectors

remember the wheel sensors are a magnet that reads the different pulses from the teeth on the ring gear on the axle/hub or on the ring gear. the computer then computes the PRI (Pulse Repetition Interval) and determines if the wheels are going the same speed. if your metallic brake dust is all over the magnet then it will not function properly.

so look at those things first, check wheel speed sensors and then go to the ABS module. for the ABS module usually the electronic part of it goes bad and can be replaced without removing the whole module or disconnecting any brakes lines. your brake pedal will also be squishier when the ABS NON-OP light is not on.

if your brake fluid is really dirty you will also get this feeling and you could loose ABS functionality without the light coming on. basic maintenance will solve this issue. please replace your brake fluid with approved DOT 3 brake fluid and NOT DOT 5!!!! The system was not made for DOT 5 as it is fully synthetic. i am not saying it can not take it, but it was not made for it.

hope this helps

1tufam

Thanks for the very informative response. Once I get the fresh rear under the car and get it on the road, hopefully the system will reset and turn out the lights. The system was working fine with no issues before putting a few miles on it while up on the lift. It only came about while diagnosing a very noisey torsen diff and gear set.