ABS Light

[EyExR]

When doing my rear suspension I hammered on one of my ABS sensors and ruined it. My ABS light came on (first time this ever happened). So, I replaced the sensor and still have the light on my dash. Any advice? It comes on as soon as I turn the key on and never goes away, which seems strange to me. I figured a bad sensor would only trigger a light when the car is moving... Is there an ABS system reset somewhere?

How can I test my sensors? Would a bad sensor trip a fuse or cause my relay to go bad?

[jlevie]

Troubleshooting the ABS system isn't very difficult. It is a standalone system
that only gets input data from the brake light switch, wheel sensors, and
system power. The parts of the system are the ABS module located next to the
steering column, the ABS relay mounted above the ABS module, the ABS unit in
the left front of the engine bay, and a speed sensor at each wheel.

If the ABS light comes on with ignition, but doesn't go out when the engine
starts, a wiring problem, bad module, or bad ABS relay are the likely
candidates. A failed or weak alternator will also cause this because the
system voltage won't rise enough. There is a fusible link inside the ABS relay
that can be blown. The relay can be repaired, or better yet, replaced.

If the ABS light comes on when you turn on the ignition, goes out when the
engine starts, and then comes back on before the car is moving the cause could
be a bad module, a bad ABS unit, or a wiring fault.

If the light goes out after engine start and only comes on when the car is
moving, there's a problem with one (or more) of the sensors. The simple test
to find out which sensor(s) is the cause is to disconnect all but one of the
sensors and drive the car. If the light comes on, that sensor is sending a
speed signal to the ABS and is good. Repeat with each other sensor to find the
one(s) that don't cause the light to come on. Since the ABS module has no
speed input besides the wheel sensors, if only a bad sensor is connected the
module can't tell the car is moving and thus doesn't fault on missing speed
signals from the other wheels. Once a bad speed sensor is found, if a new
sensor still doesn't work, there could be a wiring fault in that circuit or a
bad input channel in the ABS unit.

[EyExR]

Awesome reply! Thanks!

It's just strange that I never had an ABS light come on until I damaged a sensor. But what you are telling me is that even if a sensor is damaged, I wouldn't know until the car is moving... correct?

Also - when I disconnect my sensors to test, am I disconnecting the plug, or physically pulling them out of the hub body?

[jlevie]

The ABS module might be able to sense a shorted sensor, I've never tested to find out. But I know that it can only detect a missing sensor by the presence of a speed signal from one or more other wheels.

I disconnect a sensor at plug, but I doubt that it matters how you do it.

[EyExR]

Well, it's the passenger side rear that I think is buggered up. When I get home I will remove the rear seat and disconnect there, then turn the key. I hope the light goes out because that will tell me it's a bad/shorted sensor after all.

Thanks again!

I'm also wondering if a bad cluster (or SI Board) could throw an ABS light...

[EyExR]

Tonight I disconnected the battery then pulled the plug on the suspect sensor. Turn the car on and the ABS light is still there... I even swapped in a brand new SI Board. I guess my next step should be the relay?

[Buzztt]

I have the same problem, my light comes on when I turn the key and never goes out, I swapped rims the other day, that's when it started, I assume I damaged something, how do I figure out whats messed up ?

[jeffnhiscars]

If you read what Jim wrote, you have to unplug 3 sensors to test one.

[Will_NZ]

If the light comes on when you turn on the ignition and stays on, it is normally the relay up next to the ABS unit that is faulty.

To test to see if the relay is at fault, unplug it, then link together first the brown and brown/yellow and then the red and red/yellow wires of its socket. Start the engine and check that the ABS light goes out, then drive the car and check that it stays out.
Switch off the engine, pull out the wire linking the red and red/yellow, then the other one, or you will get a flat battery.

[gath]

How do you test the ABS pump it self to see if it is working and how do you bleed it after you change it?