Hi, I'm new to the forums and only one day into Jaguar ownership just got a 1993 XJ40 4.0 Sovereign!

I have a problem with the ABS it seems. The anti Lock light stay on constantly. I have a 1993 car so from what i have managed to understand so far from searching here and on the net in general it cant be the overvoltage regulator as late cars dont have them. I can hear the pump pressurizing when i turn on the ignition and the system holds pressure well taking 35-38 pumps of the brake pedal before it loses assistance and goes hard (with the ignition off). From that im assuming the pump and the accumulator are ok?

Any ideas as to what i should look at next. Was going to buy a replacement ABS ECU seeing as theyare only £20 on ebay but thought I'd ask the experts for advise before i start replacing bits.

Thanks

Paul

 

The 4.0 XJ40 has a diagnostic socket near the ABS module (boot, left rear wheel arch area). The diagnostic socket has 4 wires...
B (black)
NK (brown/pink)
RB (red/black)
NP (brown/purple)

DO NOT SHORT THE RB WIRE TO ANYTHING!!!!!!!!!!!!!!!!!!!!!!

You can obtain the ABS 'blink-codes' by jumping a wire from B to NK.

Turn the ign key to ON (Key On Engine Off)

Wait a few seconds and count the 'blinks' of the ABS light in the INST PACK.

I have not done this for about 10 years and I don't remember the code meanings but I'm sure I have them somewhere in my books from my JAGUAR DEALER YEARS.

JDS or PDU can be used to get the codes but I doubt you will find a working unit anymore.

bob gauff

 

Thanks Bob, just done it and the light flashes twice. Will see if I can find what that means online. Thanks for your help!

Paul

 

Sorry Bob didnt realise it was a long code,

I got 22, 33, 43, 77 then it stopped

Thanks

paul

 

Ok the last 3 are all related to the right rear sensor apparently which I have removed cleaned refit and took the car out for a quick drive to rest but to no avail.

33 : R/R Wheel speed sensor to CM circuit; open circuit or
trigger signal failure short circuit to ground
Wheel speed sensor failure
CM failure

43:R/R Wheel speed sensor circuit to CM; open circuit or
wheel speed comparison failure or no signal short circuit to ground
Incorrect wheel speed sensor to reluctor air gap
Wheel speed sensor failure
CM failure

77:R/R Sensor to CM ground circuit (shielding); high resistance or
speed continuity signal failure open circuit
CM ground circuit; open circuit or high resistance
Axle vibration, incorrect bearing clearance or sensor air gap
Refer to DTC 37
CM failure

I found a right rear sensor on ebay for £25 so I have bought that will see if if fixes the when it arrives.

22 is apparently caused by either
Valve to CM circuit; open circuit, short circuit to ground or
B+ voltage
Valve failure
Control Module Failure

Out of those I would think the most likely (and cheapest to buy) would be the control module, found one of those on Ebay too so £10 incl postage so will see what difference that makes when it arrives. if that doesnt fix it then its out with the multimeter and checking lots of wiring for shorts .

Thanks for the help

Paul

 

You probably need a replacement rear sensor/harness assy.
Pull up the rear seat and find the connectors.

You could try to check continuity for both then compare readings.
A significant difference would indicate a faulty sensor assy.
The rear bearings also fail and damage the sensors so you might pull it out and check for that.

bob gauff

 

Thanks Bob, rear sensor came in the post this morning, fitted it and the light went straight out after the initial test light up. Rechecked for error codes and nothing coming up. Thanks for your help, without you I'd have ended up replacing all four sensors. looks like I wont need the ECU I ordered so that can go back on Ebay (or possibly in my parts store :-)

Paul