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I think my ABS computer is fried… Like an idiot I did some welding and forgot to remove it. Glad I remebered the ECU
Anyway, the system does not work. Light is on continuously.
Anyone have one laying around that they don’t neeed?
My car is an 89 if that matters?
Thanks!
Troubleshooting the ABS system isn’t very difficult. It is a stand alone
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 wheel 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 wriing fault in that circuit or a
bad input channel in the ABS unit.
Levie, another cause for “If the light goes out after engine start and only comes on when the car is moving” is a bad pump relay.
First thing I’d check is the relay Jim mentioned. The one clipped to the ABS brain. Pop the metal cover off, and check the fuse (it’s one strand of copper soldered between to parts of the relay). This typically blows when you jump start the car. Welding might do it as well. Also, make sure that the metal housing of this relay is insulated from all the innards, as this will cause the same sypmtoms as a blown fuse.
Good luck.
Guys, as usual thanks for the quick replies :cheer:
I believe that I checked the relay last year and the fuse was intact - I will check again.
If that checks out, and alternator output, then I’ll try a replacement abs brain.
Rob & 87isMan thanks very much - I’ll be in touch