Hey there, I'm a new owner of a 88 XJ6 sovereign. Hopefully I'm not disrespecting, but my plan for the car is to pull the motor and trans out and replace it with a GM lsx motor. I really like the look of Jaguars and my goal is to have a powerful luxury car to cruise.

The car is in amazing condition. The interior and exterior are practically new. All that aside, I'm having an issue with the ABS. I keep getting the "antilock brake failure" in the instrument cluster. I'm not really experiencing any negative symptoms though. The brakes feel fine to me. The fault comes up after I hit about 30mph. Sometimes I can drive for miles without the fault. I noticed I'm not always pressing the brake when the fault sets. Also, very very rarely I will get a "low brake pressure" message.

I've done some research and read about some common issues. I soldered the joints in the "over-volt abs relay" because they looked cracked but didn't fix it. I used an oscilloscope on all 4 wheel speed sensors (at sensor connector) and they are all showing good wave patterns. I was thinking I should test each speed sensor at the module to rule out any wiring problems. Do you guys have any suggestions?

 

I would double check the solder joints on the ABS relay... better still, get a new one...

Also, remove each wheel and give the speed sensors a good clean with brake cleaner...

If the problem still exists, then you'll have to carefully inspect the hydraulic system for any leaks... and you may also want to inspect the circuit boards in the instrument cluster for any possible hairline cracks of the solder joints in there

 

Thanks for the reply. I could triple check the ABS relay, but it looked fine to me. The speed sensors showed good wave patterns on the oscilloscope, but I'll go ahead and clean them anyways. I just had the instrument cluster apart because the left side digital display goes out sometimes when hot. I used a magnified glass and couldn't find any bad solder joints to fix. I don't think I have any hydraulic leaks. I've been driving the car everyday for the past 2 weeks and the brakes feel fine to me. Not loosing fluid.

I really would like to diagnose this without throwing parts at it. I have the service manuals for the car but sometimes they can be very vague. I wish I could see what the ABS module is monitoring considering the fault comes on when just driving without hitting the brake. You would think it's only looking at wheel speed sensors and adequate voltage.

 

Just adding a reply to subscribe to the post. I've got the same thing happening on my 89 sovereign, brakes work OK but the ABS failure warning comes on at odd times (not when the brakes are applied). The ABS is still working fine - I can brake without skidding on an unsealed surface, so I'm not overly concerned.
If you fix your problem, I'll have an idea what to look for.