ABS light coming on sometimes

[DmcL]

ok so my ABS light has started coming on randomly. so far it either does or does not come on when starting the car. if it comes on when starting it stays on till i turn the car off again, if it doesnt come on it also seems to stay off till the car is turned off and started again. doesnt come on every time i start the car and when it does sometimes i can turn it off and back on and the light will go out.

possible causes? dirty ABS sensor? where are the sensors and is there one on all 4 wheels? also sometimes the ABS will pulse a little when slowing down gently from a low speed roll of like 5mph or less.

need it to not come on for inspection on monday evening. i couldnt care if its on 24/7 after that just need it to remain off after starting the car (2-3 times) at the inspection centre monday evening. also must survive being put on rollers for brake strength/balance tests tho atm it doesnt seem to come on any other time than when first starting the car if its going to come on at all..

[draccent]

Pull the abs fuse so the light doesn't come on during inspection. If they do a visual inspection, then clip one blade off the fuse and stick it back in the holder. The fuse will look fine, but you won't have to worry about a light.


Now...onto fixing things. ABS sensors are located in the rear on the passenger side, and in the front on the drivers side. I am almost positive that you don't have a sensor for every side.

[DmcL]

yea i seemed to remember something about the ABS sensors only being on one side in the front/back.

if i pull the fuse or clip off a blade the light wont come on at all tho and i need it to come on and go back out like it would normally so unless i pulled the fuse and wired the ABS light off of one of the other dash lights that come on/go out at start up.. id like to try cleaning the sensors first and foremost because the ABS does seem to work fine and all that tho this is a new problem and only started the other day. im hoping its dirt/gunk related and maybe the sensors just need cleaned off.

[draccent]

See what you mean, in that case I would go for trying to clean up the sensors and see what happens. Be sure you clean the actual electrical connector too.

[DmcL]

thats the plan.. hopefully it will solve the problem atleast temporarily. think its too late to cancel the booking and get it changed to a later date so not really any time to go ordering and waiting for new sensors, etc, etc.

[djb2]

If the light sometimes stays on after starting, the ABS is not passing the self-test.

The typical problem is low system voltage -- is the alternator generating full voltage immediately after starting? Check with a voltmeter.

The system self-test involves cycling the pump just after starting. It needs full voltage to do this. If the alternator isn't generating power, and especially if the battery is already weak, this test will occasionally fail.

To forestall incorrect suggestions: this problem is different than a blown over-voltage protection relay (which would always leave the warning light on permanently) or a metal dust clogged wheel sensor (which triggers a fault only when you start moving).

[barbierij]

Ooh you are lucky the iX has 4 wheel sensors and 2 body sensors for the ABS. Plus they are about 3x as expensive.

[DmcL]

it seems to re-do the self test or something when stationary. i can hear the pump buzzing and if i press the brake the pedal pulses once or twice then goes back to normal.

battery was replaced with a new heavy duty one less than 2 months ago due to cold startign issues and a weak battery and the ABS never did this. no starting trouble but seems to happen when colder..

[///AlpinePower]

it seems to re-do the self test or something when stationary. i can hear the pump buzzing and if i press the brake the pedal pulses once or twice then goes back to normal.

battery was replaced with a new heavy duty one less than 2 months ago due to cold startign issues and a weak battery and the ABS never did this. no starting trouble but seems to happen when colder..

I have the same problem (on an E36 M3) - my ABS light comes on after POST if the car has been sitting. If I roll the car, or run it, or tap the brake pedal, I can restart the car without the light coming on. Ever find a solution?

My OBC reads battery voltage right at 12V and when running between 13-14V