Hi Pegleg
I have a xj 40 1988, vcm is showing low brake pads, has been checked by brake machanic all check out as plenty of pad. What can I check?, .can I disable them
The abs warning light is coming on. can I clean the sensors on the wheel? and if so what with?
Here in Australia NSW, an unregistered car has to have, what we call a blue slip, so will the check garage fail the test if the vcm is showing warning even though plenty of meat on pads. If abs will it fail test.
On your '88, the brake pad wear warning circuit is in effect a continuous wire from the instrument panel through each of the four brake pads in tuirn and back to the instrument panel. If that circuit is broken / open circuit or any part of it grounded (as it would be on a worn pad grounding the embedded wire to the brake disc) then the pad warning will appear on the panel.
If you ensure there is continuity in that circuit (if necessary by manually re-connecting / connecting together any broken bits of the wire) and that it is not grounded anywhere between the wheels and the instrument panel, the warning light should extinguish.
As regards the ABS warning - that is an automatic ‘fail’ in the UK. There are a number of possible causes, discussed extensively in the forum archives, favorite on the early models being the ABS over-voltage relay in the boot. The ABS wheel sensors are prone to corrosion and sometimes impossible to remove without damaging them but they can be tested in-situ - search XJ40 archives for description of how to do that similar to this post:-
Here’s how i would go about troubleshooting your problems:
First take off one wheel at a time. With the wheel off now remove the wheel speed sensor (it’s only held on by one bolt) and give it a good cleaning. There’s no need to unplug the electrical connection. Any good degreaser and a toothbrush should do the trick.
While you still have the wheel off unplug the brake pad sensor connector. Using a multimeter check for continuity between the two wires going to the sensor at the connector. If you have an open circuit that’s your problem. Remember, the brake pad warning has nothing to do with the physical thickness of the pad. It’s the wire in the pad that riggers the signal. If all 4 sensors show continuity (or short) then your problem is further up stream.
When you finish cleaning all 4 speed sensors do you still have an ABS warning ? If so now move on to the ABS over voltage relay. On my '89 that sensor is located in the trunk under the fuel filler pipe. Remove the relay and using two jumper wires apply 12v to pins 86 and 31b. You should hear and feel a slight click. Iif you don’t feel the click, while still applying the 12 volts check for continuity between pins 30 and 30a. No click or continuity and you’ve just discovered the cause of your antilock failure (ABS) warning light.
If this test failed then you have a bad relay (and these things are a bit pricey, around $65) but lets try and fix this one. Open the relay, which will probably involve cutting away the sealing material and check the internal fuse hasn’t blown. This fuse may actually be a glass fuse or just a short piece of fuse wire. If the fuse is good the next thing to do is reflow the solder joints on the printed circuit board side and retry the test with the 12v jumper wires. Hopefully this should do it.
Thanks for your advice.
Have cleaned ABS sensors and checked relay it to be seems ok still getting warning. In the engine bay the electrical connectors from the ABS sensors have become brittle and pieces are falling off exposing wires. Will talk to my auto electrician to-day to make up new connectors.
Have not checked brake pads continuity yet.
Thanks Pegleg.
Sorry another question can I disable the ABS warning for registration purposes ?
Thanks Pegleg.
“checked relay and it seemed to be ok” … seemed … umm, did it check ok or not ?
I’m still guessing if you do a complete proper check of the relay you’ll find it’s at fault.
Not if you live in the UK you can’t. For its inspection, if the car came from the factory with an ABS warning system on which the light illuminates during the ‘bulb check’ phase when you first switch on the ignition and then extinguishes after it has completed its checks, the inspector needs to see the light do that or you get a fail.
Hi Pegleg
Re abs connectors in engine bay have become brittle and coming apart got some bullet type connectors today will they be ok to use?
Thanks Pegleg.
Hi Pegleg again where would find the plug /connector for the scan tool? on the xj40
Thanks Pegleg.
Sorry XJ40 is OBD1, you would have to have the contemporary Jaguar software to read deeper than the VCM can give you.
Have you pulled codes from the VCM?
Pegleg
No, how do you get the codes?
Thanks Pegleg
From memory, and its a long time since I had my ’88 you run the engine and then turn off the engine but do not turn the key fully off, once in this position depress the VCM button and record the letters and numbers on the dash display.
Hi Pegleg, I think the full list of codes and what they mean can be found in ‘The xj40 book’ on here. Usually two letters and a number, FF 23 for example, but any stored codes are erased if the battery has been disconnected.
Hey Casso - The XJ40 e-book has limited codes listed and none? for an '88 (which I believe only has about 8 in total?) …even the problematic FF 23 you mention doesn’t appear in the e-Book!!
We really need to update the XJ40 e-Book one of these days!!
here’s the 88MY fault codes:
Pegleg here
Had relay checked today, there were dry solder joints in it. Have not placed in car yet.
Thank you.
Pegleg.
You’re more than welcome. Hope that solves your “Antilock Failure” warning light. Let us know.
Thanks Bryan
Have checked all pads, all giving continuity at the wheels still getting low pad warning where to now.
Thank you .
Pegleg.
OK, so you have continuity through each pad - but did you check if any of those wires also went to ground (usually on the rotor)?
If all the pads and their wiring is sound then you need to check continuity/grounding on the rest of the wiring up to the instrument panel. There are perhaps 3 or 4 connectors between the pads and the panel. The one at the instrument panel is a 36-way black connector (LB54) under the left side dash. With everything else reconnected, if you disconnect that and check continuity between pin 2 (Orange/brown wire) and pin 3 (Orange/slate wire) and check that neither go to ground, the wiring up to the panel must be OK. If open circuit or grounding then the fault must be further downstream and will require extensive investigation of the connectors and wiring.
Thanks Bryan
The car is going for a registration check on Tuesday, so see what happens after the test.
Thank you
Pegleg.