Oh did I have "fun" for 2 days now: After working on my S-Type for 4 month (since I bought it) and everything "should be apples" by now, I had 2 simultaneous messages on the dash: "ABS fault" and "Cruise control not available". Obviously, while working on the Jag for such a long time I did have the battery disconnected for very long periods. But I periodically recharged my battery with one of my CTEK chargers, so the battery was happy.

I thought about possibly asking here for advise, but I refrained from it, because I knew, what the replies would be: "It's the battery", "+1 battery", "+2 battery", "flat battery". And this is pretty much what I got anyway, when I just mentioned my issue in different context in another tread, even after writing before any comments could come in: "And no: It's not the battery"... I also received the Monty Python clip "Bring out the dead": "I'm not dead, I am getting better" to which I replied (for Monty Python fans): "(Only) ONE BATTEWY EACH!"

Now, I do not doubt that many funny faults can be explained with a dying battery, but in my case I was sure that mine are fine - but just for the sake of it I double-checked: I am getting the fault messages reg. ABS and Cruise with my 13V battery, which was in there and also with the 12.9V battery from another Jag. So: "It really is not dead yet!" "It is invincible" - just like the Black Knight in Monty Python - due to regular recharging.

So when I first saw the message "ABS fault" I was not overly worried, figuring that there is a very high chance that one or both rear wheel ABS sensors "retired themselves". As I had time, I simply ordered 2 from Aliexpress. P/N: XR822753 (for S-Type 2002 to 2008 from VIN M45255 / and for other Jags), currently AU$12.98 each.


Those connectors to the ABS speed sensors on the rear axle are a bit tricky to open. The connectors on the left and right are identical, i.e. on one side, the red "pin" needs to be pushed outwards, on the other side inwards.


This is being done with a screwdriver.


After that pin has been pushed thru it is extremely easy to lift the connector off.


And this is that connector. I measured (with ignition on) the full battery voltage between those 2 pins, which tells me that the wiring is OK. And when you reconnect them way later to the new sensors, you might have forgotten about those red pin meanwhile altogether and you get the impression that your connectors are broken. But when you then remember those red pins, just push them in again after positioning the connector over the sensor and Bob's your uncle...


Here I measure 2.5 Mega Ohm on each of the brand new sensors. One old one measured 0.7MOhm and the other one started the measurement at that same level, but quickly went down to zero MOhm. I assume one or the other was broken. Anyway, I had now the new sensors.


ANNOYINGLY the ABS & Cruise faults were still there. In my extensive research on the net I saw that it is possible that the PCB of the ABS/DSC-module (the elk-test-module ) could have cold welds in need of re-welding. Thus, I actually managed the near impossible (as there is no space at all) to remove the black-box DSC-module from the "octopus", without actually removing any brake-lines...


...but there is not much point in explaining exactly how I did that, because this was a pointless exercise: On the S-Type that DSC-module cannot be opened and I cannot access the PCB. Thus, I put it straight back on. I think what I saw on the net regarding that PCB must have been on the XJ8...

Thus, 2 perfectly good days wasted and I still had the ABS and the cruise fault.
I just mention here all the other possible things worth checking in this situation: Check, of the connector-contacts on both sides of the rear speed sensors are not corroded and do not have humidity inside (I could not have had that problem). Always a good idea to check for the battery cables as well (others had issues with broken cables). Check for water in the boot. Check if those "rings" on the rear axle, which the speed sensors "read", are undamaged and clean. Well, yes, and (see top of my thread), make sure, your battery is not dying...

So I was pretty much at my whit's end, but always having in the back of my head one very last and very simple thing, which needed testing...:
"Just drive, she said!" (Stan Ridgway / 1986).

These fault messages were on the dash-display ONLY. And those messages were there, although the Jag had not been driven. There was nothing at all wrong when I checked with my OBDII-diagnostic. That was fishy from the onset. I considered all along that moving the car would hopefully "initialize" the system with the new sensors, or simply reset the system after that very long time, when the battery was disconnected. Thus, I already drove a few times those 4m forwards and 4m backwards.

I just was not too keen on driving the Jag on the road without rego (TUEV / MOT). On the other hand: I should actually be fine if the police would stop me, because the regulation here is: I am allowed to drive without rego (without plates), if it for the purpose of doing something necessary to obtain the blue-slip (=rego)...
So I drove on the road and after less that 50m those error messages were gone. Stopping. Engine off. Restart - still gone. Thus, if the police would have stopped me, I would have had to tell them: I have to drive the Jag to fix it - it would have been the truth - but I am not sure, how my chances would have been that they would have believed me...

Summing it up: I am not sure, if the system had to get friends with the new sensors first, or if the system need a bit of a drive because the battery was disconnected for a very long time - but driving the Jag a bit solved the problem. Somewhere I even read that I have to drive 16km at different speeds. That was not the case. 50m rolling along was just fine - and now Bob's your uncle. I also read that it is logical that I had that "Cruise control not available" message, if I have the "ABS fault" message, as the Cruise control uses the ABS/speed sensors.

When I mentioned in that other thread that I am currently working on that issue with those fault message at the moment, I was asked, if I also had the handbrake fault message... well, no, unless the question was, if I also have the message, which related somehow to hand- and footbrake. I figured that one out: Every time you have the battery disconnected for more then a few minutes, you get that, but it is easy to deal with: You step on the footbrake, keep stepping on it, apply the handbrake and then release it (or the other way round), and then let the foot-brake go. This is to reset the handbrake.

While doing all this, I also just figured out that my diagnostic allows me to release the el. handbrake for the purpose of changing the brake pads. When I did it back then, I did a bit of trickery, but this is apparently, how you do it properly, and not like a guy on youtube, who needed a very long time to change the pads, because he was very busy cursing the electric handbrake...

Also, I saw many times that one should make sure that the Radio-code is at hand before disconnecting the battery. Well, I have it, but my radio never wanted it...

 

If you have a good battery and are getting no abs, no traction control, etc messages, if you can find a mechanic who has the right device for diagnosing problems and knows how to use it, he can see how everything is working in real time on the car, while you take him for a ride and the car will tell him which speed sensor or other component is causing the problem. The wiring on the S Type is excellent and the fault is almost always the sensor itself, not the wiring. When my battery was going out, the car was like HAL going down on 2001, randomly spouting off problems and the gauges waving around.

 

There is another potential root cause for problems I intended to list in my thread above, but forgot, but now I can even describe the issue on an example...

This is regarding the battery: CLEAN THE CONTACT SURFACES.

Yesterday I wanted to use my ride-on mover after not using it for a few month. I periodically recharged it with one of my CTEK chargers.

Btw.: I have 2 CTEK chargers, one with 7A, which is just a little bit on the weak side when it comes to charging a huge Jag battery (but just works), and the other one has 15A, which is a bit over the top - thus, if you are in the market for one: Look for something between 7A and 15A.

When I wanted to start my ride-on mower, the electrics seemed to work, and the electric starter kicked in for a second (each attempt), followed by painful humming noises and no more movement. After a short while I figured it out: Corrosion between the contact-lugs of the battery-cables towards the battery.

Yes, that explains it: corrosion on contacts means: quite a bit of electrical resistance. This has the effect that you have full battery voltage, but as soon as there is a huge power-demand (from the starter), it cannot be delivered, because due to the increased resistance the current is severely restricted (P = U x I or P = I² / R).
I even placed a second battery in parallel with starter cables, but that did not help, because the power (current) is still restricted by that corroded surface towards the lugs of the battery cable. Thus: I removed the corrosion with a wire-brush on the drill and problem solved.

This means for the Jaguar: Clean (with some kind of wire brush or sandpaper) the battery terminals, the connections on the cables and the connection of the earth (ground) cable towards the body of the Jag (i.e. unscrew it, clean it and apply WD40 or similar).

 

Yes you will still get the dash warnings regarding wheel speed sensors until the car is driven.
These sensors provide a pulse to the control unit. The only way this can be tested is to drive the car.

Most general OBDII diagnostic units will not read the Jaguar ABS codes.
You need to get one that does, or use the Jaguar software and dedicated interface.

Mellow

 

While I did not have too many issues with my Jags which would result into OBDII-reader error messages, the one code I had, was displayed on my reader (which did cost around AU$500) - that was on my XJ8, telling me that the restricted mode is due to defective knock-sensors - I replaced the sensors, issue solved. Also, I can release the el. handbrake of the S-Type with my reader, i.e. that reader is able to communicate with the S-Type.
Yes, that was what I verified: That ABS fault clears only after driving - and not as I had hoped initially - driving 4m (meters, not mls) forward and backwards...

 

A lot of ABS controllers need the car above some threshold speed (4mph or whatever) so the controller sees all the sensor signals long enough.