You guys are good, so here is my next problem that I would like to diagnose and fix. The ABS warning light on my 1995 XJS comes on when I start the car and then goes out. After driving about 200 - 300 feet the warning light comes on and stays on.
If I understand the system correctly, this sequence indicates that the ABS unit is good but one or more of the wheel sensors is not being seen by the ABS control computer.
I plan to remove each sensor and clean it when I have time. Is there also a normal resistance that the sensor should read that I can use to isolate a possible failed sensor?

And if I am totally off base, please guide me in this.

Thanks.

 

This is normal,

I think you are on the right track here. The ABS light indicates the ABS ECU has switched the ABS control off. If your brake light is off then the normal brake system is still ok.

As you say - start with cleaning the sensors, or make sure nothing is interfering with the sensor on the emitter. Aslo check the gap between the sensor and emitter this is critical as the further away from the wheel the sensor is the lower the generated voltage will be. Check that the tip of the sensor is not damaged.

I could not find any spec for a DC resistance but looking at the type of sensor I would expect them to be in the 1-5 Ohm range. Best way here is to check all sensors and verify that they are all around the same resistance.

The fronts are PITA to get at, when I re-assembled my front end I forgot to reinstall the ABS sensors and had to remove the lower shock mount to get the darn things in.

Easiest way to get them out is jack the car and secure with stands, then remove wheels.

Disconnect the sway bar and remove the lower shock and swaybar mount.

The sensors generate a sign wave so if you have a meter (or scope) you could meter each sensor and spin the wheel by hand, the frequency should increase as the wheel turns faster

 

Good info. I appreciate the suggestions and will pursue, hopefully this weekend. I will post what I find.

Thanks.