I think many people have sooner or later the issue that the ABS warning light on the dash does not go off anymore.
While that means that the car still brakes, it also means that the ABS function is not active anymore.
In my eyes that's not an issue...: After all there were very powerful cars on the road before ABS had been invented. However, "rego" in Australia (=MOT / TUEV / technical check-up) does not see it that way and this would be a fail.

I am working on that 2.5L AWD 2004 X-Type since 4 month now (it was utterly neglected when I bought it), and after all that I would have failed rego next month with that ABS light on...
Hence, my goal for today was to fix this - and I did.

I searched the net for a solution, not just looking for an X-Type solution, but I looked for any ABS light solution. The suggested solutions are plenty and while some of those solutions may work for others, it did not work for me:

SO HERE IS A LONG LIST OF SUGGESTED SOLUTIONS, WHICH ALL DID NOT WORK FOR ME (but some of them might still me of use for others):

Actually one solution worked for me on my X308 (that ABS light stays on after disconnection the battery and reconnection it). That solution is simply: Drive, and it fixes itself.

Frequent suggestion is to let the OBDII-scanner look for the issue. I have one. It did not show any issues. I just read somewhere that cheap scanners do not check out the speed-sensors. Well, my scanner was not cheap, and I am not going to but another scanner to see, if that works any better.

A frequent issue is dirt between the sprocket-like teeth passing the speed sensor, which cause the movement of the electrons in the coil in the speed sensor. But that definitely was not my issue, as I had just cleaned everything.

I actually thought that the ABS light did not stay on before my various repairs, including brake fluid change. Hence, I was kind of convinced that the issue is air being trapped in the ABS unit, and I kept focusing on that as a problem. With the air being trapped in there the pump in there would not do anything or not even attempt to do anything. I read that a real expensive scanner is required, where you can force the ABS pump to move so that the air gets moved out of there. Since I do not have such a scanner, I thought a vacuum handpump, with which brake fluid is supposedly being pulled out of the bleeder-nipple, would do the trick. I bought one. This thing is utterly useless. Did not work as intended for some reason. I simply did some more "normal brake bleeding" (thin hose over bleeder nipple stuck into an old milk bottle, which already contains a bit of old brake fluid - the hose end needs to be below fluid-level. And with a nipple a tiny bit opened, you can press the brake pedal yourself without needing a second person). That done, my ABS light still did not go off. I also tested the other suggestion to find a gravel road and go there and brake several times (to remove the air from the ABS unit). But this also did not do anything other than utterly covering my car in dirt-dust. Well, after all that I had to accept that air in the system is probably not my problem.

Next: Looks like there are several different kinds of ABS sensor systems. At some of them you can pull the connector off the sensor and measure (with ignition on) between one of the pins going to the sensor and battery-minus a 12VDC voltage. But not on the X-Type. Different system apparently.

SO AFTER ALL THAT, THIS WAS THE LAST AVENUE LEFT TO FIND A FAULT IN THE SYSTEM:
I started to measure electric resistance on both:
1. Between those two pins of the connector going to the speed-sensors and
2. Then between the two pins on the speed sensor itself
The idea was to discover any difference between the 4 sensors on the 4 wheels...:

I started on the right front: Negative result in both occasions: Unlimited resistance on the incoming cable and on the sensor. From there I had not much hope left, but I continued anyway:
I did the same on the left front. And success: While there was again nothing I could measure on the sensor itself, the TWO PINS ON THE CABLE GOING TO THE SPEED SENSOR MEASURED JUST SHORT OF 700 OHM!!!! EURECA! That most certainly was the difference I was looking for. So the problem was the front right! I re-assembled the front left and disassembled the front right again and confirmed again: No really: Nothing like 700 Ohm there between the pins of the cable to the sensor on the front right. Thus, I had to see, where this cable is going. I had to remove the rear part of the wheel-liner on the front right. Behind that I found that this cable is going into another connector - see:


That's the connector behind the wheel-liner. On the right is continues on to the speed sensor.


Somehow I managed to get that connector off. Using a heat gun, I then also managed to get that clip out of the "wall" (without heat gun, the clip would break), as I would not be able to slide the connector back on with the clip still attached to the wall (but I am getting ahead of myself - that is important later for re-assembly).


SO THIS IS THE PROBLEM: CORROSION OF THOSE CONTACTS IN THAT HIDDEN CONNECTOR!!! CORROSION MEANS: NO ELECTRIC CONTACT = THE INFORMATION FROM THE SPEED SENSOR DOES NOT GET PASSED ON = ABS SYSTEM FAULT! How silly is it to have a connector there at all in the first place instead of having a cable going all the way thru. This is a design-fault and a design-failure waiting to happen! After cleaning the corroded contact with contact cleaner, and a few minutes later forcing the surface contamination off with compressed air, I sprayed a bit of WD40 onto the contacts and then connected that (hidden connector" back again. And yes: As you can see above, NOW I can measure those close to 700 Ohm on the connector going to the speed sensor. And when I connected that connector to the speed sensor, I turned on the ignition... AND THE ABS LIGHT WENT OFF after the initial few seconds as intended.

Now I can dare to present my Jag to the technical check-up.

PS1: I only use since very recently "contact cleaner" spray. In the past I would have simply used a wire brush to clean the contacts (which I forgot this time - I should have done both before applying WD40).

PS2: Of course the same corrosion problem, which I had here could also have occurred between speed sensor and its connector. But not in my case, as I cleaned all those contacts already without knowing that I had an ABS problem, and I also removed those sensors to clean in those apertures below in line with my routine after buying a used Jaguar.

PS3: When I was totally fixated on then idea that my problem is air being caught in the ABS unit, I already came up with the idea to connect a pipe to the brake bleeder nipple, the other end thru a press fit hole of a lid of a jar, a second pipe into a second press fit hole of the jar-lid and on to a vacuum cleaner... But after the attempt of using the hand-held vacuum pump went to very poorly (it sucked in a lot of air-bubbles and no fluid from an only slightly opened bleeder nipple - and the air was not in the brake fluid - it came from between the bleeder nipple and the brake-caliper (air-leak)), I skipped that idea with the vacuum cleaner. Plus, I had given up my fixation on the root-cause being air being caught (it is not easy to give up a wrong idea, once you have it in your head...).

PS4: When searching the net you will also come across suggestions that your ABS unit might be damaged that that you need a new one... - I am not saying that this is absolutely impossible, but the probability, that that is the problem and not one of the many other possibilities, is very low.

 

What I wrote above should definitely have solved my problem, but there was more to that story...

I HAD TO GO TO CRAZY-LAND AND BACK TO FINALLY SOLVE THAT PROBLEM - which was - as I assume now - due to intermittent contacts at two different locations "in the same line"...

So after fixing this as above I drove about 2k's until the ABS-bulb kept smirking at me again.
Thus, wheel and half of the wheel-arch-liner off again, I cleaned that contact again - more thorough this time and I was convinced that I pulled some blue corroded material out there and I applied CRC 2.26 contact spray. ABS light off... - for another 2k's.

Challenge accepted:

I gave that connector the boot, i.e. I kicked it out and I soldered in 2 bits of wire of the same length to replace it... Guess what: Good for another 2k's until the ABS light went into party-mode again... BTW: Whenever I fixed it, I confirmed that there are those 600-700 Ohms on the connector to the speed-sensor / and whenever the ABS light was back in party-mode, there was again unlimited resistance on that same connector. So I knew I was digging at the right spot, but somehow I was missing the spat marked with an "X", where the gold was burried...


Next drastic measure: bypassing red/brown wire from where the connector was before to just before the big blue connector (I measured and I confirmed in the electric diagram, that red brown wire goes to pin 15 in the big blue connector).


To be able to measure and confirm, where the wire goes, I taped a needle to the red measuring end of the multimeter, which I could stick nicely into the connector. Hence, that questionable red-brown wire is now replaced .. AND THE ABS PARTY LIGHT lit up again after 2k's....


Perfect contact, as you can see...


Having traveled now that deep into CRAZY-LAND, I just proceeded one step further: Taking the big blue connector apart: That purple cover lifts off quite easily when poking with a very small screwdriver into those 3 latches with the black clips. The front right speed sensor connects to pin 15 and pin 16.


The black back cover also comes off very easy after pushing in the two latches with a very small screwdriver. Also: There was a cable-tie at the "cable-end" of that connector. to get the black cover off, one would normaly have to cut that cable tie off (carefully - not to damage any wires), but the plastic of the cable-tie was that brittle (due to the heat in the engine compartment) that I could simply break it off...


I use here the needle on my multimeter-"feeler" to push back the blue tiny latch that holds the hollow connector-pin in position 15 and I press with a tiny screwdriver against that connector-pin to push it out.


With that connector-pin pushed out, I could connect it now on its own onto its opposing pin in the black connector-base of the ABS-unit (octopus). Purpose of that was, to get a feeling for how it sits on that pin - and it was very loose. LOOSE CONTACT BETWEEN THE HOLLOW PIN AND THE OPPOSING PIN MEANS: INTERMEDIATE CONTACT! Trying to bend that pin on the wire was a no go.


Thus, if I cannot make the hollow pin on the wire narrower, I have to make pin 15 of the octopus a bit bigger in diameter. I heated up a soldering ion and each time before I used it to apply a tiny bit of solder onto that pin 15, I disconnected it from the power-grid, - I am over-cautious there avoiding that sparks on the grid could damage the electronics in the octopus.. After each go I checked the fit of the hollow pin - and the solder was too think, too thin, too thick - so while I know now, what the issue was, it would have been a bit tricky to do without taking that connector apart and just putting a bit of solder onto pin 15 of the octopus, because to start with, I would never have been able to gat a feel of how loose it was before and to find out, if it is right now (with too much solder on, I could probably damage the connector, when attaching it later as a whole.

Thus, the hollow pin 15 (of the big blue connector) sits now firmly on its counter part (pin 15 of the black octopus connector). And while I did not drive my "2k's" yet, I am very confident that this is it now and the problem is solved. No more ABS disco-lights.

And as this issue could materialize at any pin (even though the Company Delphi, which hade the connector, is a pretty good one), here is a list of where all the other speed sensors connect to (I checked this our on the circuit diagram) - and I checked it out on the circuit diagram for the 2003/2004 X-Type (I do not know, if the following is true for all X-Type):
Wheel speed sensor FRONT LH goes to pin 12 and 28 of the big blue connector of the octopus, which is called "JB45" in the circuit diagram.
Wheel speed sensor FRONT RH goes to pin 15 and 16 of the big blue connector of the octopus, which is called "JB45" in the circuit diagram.
Wheel speed sensor REAR LH goes to pin 13 and 14 of the big blue connector of the octopus, which is called "JB45" in the circuit diagram.
Wheel speed sensor REAR RH goes to pin 30 and 31 of the big blue connector of the octopus, which is called "JB45" in the circuit diagram.

 

Excellent detective and repair work, Peter!

Many times when I run into a connection problem like this I use very small needle nose pliers to twist the male pin ever so slightly so that it scrapes the female part of the connector when it is plugged in.

 

Thanks Larry, that would have been an option, too. I'll remember that for next time. I just did not have any such issue before...

That is: I actually did that on the connector, which I then cut out: At the second attempt to fix the inline connector (thinking that this is the culprit) I have not only cleaned the connector pins (and receptors) I also bend the round pins slightly outwards (twisting round pins is obviously not an option). But I never had huge pins like those of the octopus failing - even the idea of that still seems mad to me, hence it was so tricky to find...

 

To remain accurate about how I fixed this "ABS light on"-issue I have to add one more thing:
Well, above could really have been the solution for the problem, where I placed a bit of solder on the pin on the ABS-module-side.
Because as I know now, the problem was really that the "hollow" pin in position 15 in the big blue connector did not have proper electrical contact to the pin in position 15 on the module side. But as I had to find out, the "tinning" of that pin STILL did NOT solve the issue: The ABS light came on again after a while. But now I have really solved this problem, which was indeed due to improper electrical contact between the 2 opposing pins in position 15.

I solved this now finally by replacing the "hollow" pin in position 15 in the blue connector side. I had bought some time ago some connectors on Aliexpress - 4 pin connectors and they came kind of like as a "puzzle" - all the parts were delivered to put those connectors together yourself, and I just took one of those "hollow" pins from those connectors:


I think I used tiny screwdriver (or needle) to move the plastic bit to the side, which held the original "hollow" pin 15 in position, so that I could push the original pin out of the connector. Next I extended the wire-length a bit and soldered the new "hollow" pin onto that extension and pressed the new pin back into it's position.


It's easy to see, which pin looks different - but that is only, because the pins is of slightly different design. With that new pin, I finally had achieved proper electrical contact and no more ABS light on. That nut was really hard to crack!

 

Thank you for this detailed explanation! I've been fighting the ABS light for some months now on my x-type '02 - 2.5 AWD. Changed the speed sensors, oil, bearings, almost everything...Next thing on my list is that cable between sensor and Abs module. I have a good feeling about this!

 

Good. It is m ore likely that the issue is somewhere with a connector rather than the cable itself.
It's such a silly little detail, but with that ABS light being on it is - at least here in Australia - not possible to pass rego (i.e. to pass MOT / TUEV).
During my last rego check I somehow managed to keep the ABS light off for those 15 minutes during the rego check (by luck), but soon after I found the real issue - one pin on the connector to the module) and now it is really fixed. The ABS light did not come on anymore - it is really fixed.

 

Actually that light bothers me personally, no reg.issues in my country but, I like to have my Abs and cruise control operational.
I'm sure it's a connection issue because I drove my car for many kilometers on the highway and everything was ok, as soon as I hit some bumps or car body moves a bit on a bad road, Abs light goes on! Anyway I will update you here and thanks again!