Jaguar XJ40 ABS problem

Hi everyone,

I have read all the topics I can find about ABS on Jaguar 80’ but I would like to know your opinion…

I have a Jaguar XJ40 from 1989 and there is some problems with ABS (seems to be common on those cars). Before ignition, I have the message “Antilock Failure” but disapear on road. I have read it can be the Overvoltage relay. The strange part is that when someone goes on the back seat (more weight in the back), I feel in the pedal that the ABS system is working (clac clac clac …15% of the time on the road). It’s very bizarre and happen only in this situation.
Had someone an exprience with this issue ? Can it be a rear ABS sensor ?

Thank you :slightly_smiling_face:

Not exactly sure what you are experiencing, but getting warning lights on dash before engine is started is perfectly normal - if I understand your issue, the warning light goes out once the car is running?

There is no light: only this message. Once the engine is started, no message and no problem. But if I have some weight at the back of the vehicule the ABS goes crazy :sweat_smile:

Is it possible to use the ABS auto-diagnostic like XJ40’ 1990-1994 ?

see :

Rezm …

I have the same model 1989 3.6L XJ40 as yours and I’ve had the “anti-lock failure” problem 3 times over the past 28 years.

1st time the fuse inside the ‘ABS over voltage relay’ was the problem. I replaced the internal fuse with a new one and everything was fine.

2nd time I replaced the ABS control module with a used unit and that solved the problem.

3rd time it turned out to be the ‘ABS over voltage relay’ again. This time I discovered that even though the relay was operating properly and closing, a bad solder joint wouldn’t allow current to flow through it.

I think I’d start my troubleshooting there and if that doesn’t solve the problem move on to the wheel sensors.

Thank you very much for your responses !!!
I will start there @Grooveman