91 Q45 ABS clunk on backup - Light on intermittently

[trw2k]

91 Q45 212,000 miles, runs great.
The ABS light recently came on.
It comes on usually after a few seconds after starting.
It stays on until I shut the car off.

Prior to it ever coming on whenever I would back down my driveway I would hear and feel one slight clunk. This clunk seemed to come from the master cylinder or that general area. I could feel the pedal sort of give when this would happen but the brakes would still work. That was the only time it would do it...backing down the driveway gently applying the brakes.

Ever since the light has been coming on this clunking stopped.
This morning I felt the clunk and the ABS light never went on.

I have run the diagnostics for the relays and they seem fine. The control module gave me a code 9 and following that led me to either the control module is bad or the Actuator.

So...what are your thoughts?

[Q451990]

The clunk you describe is the normal ABS self test. It's most noticeable backing down a hill.

The "normal" failure mode for the actuators is that they start to leak. I have never heard of a bad controller or ABS actuator that's not functioning... but at this age anything is fair game.

Have you tried replacing the relays under the black box on top of the actuator? I'm pretty sure they're just standard automotive relays and would be available at your local parts store (like Autozone).

Heath

[trw2k]

Thanks Heath!
I will try that.
I went through the diagnostics with the sheet you sent me and the relays seemed fine....but I will try replacing them.

[Q451990]

Did your ebay service manual show up yet?

Heath

[trw2k]

It did show up...could have got one for 1/2 as much if I would have searched using "q45 manual" instead of "q45 fsm" but live and learn I guess.
It is going to come in handy as I have quite a few random things that need fixing on this car.

Tim