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Ron, fix the CAN bus wires. It could be simply that the ABS module is not sending that pressure and it is causing the code to pop up. I would need to look at the code sheets I have and see what the relationship is between the two codes (P1637 and C1440).
Ron, fix the CAN bus wires. It could be simply that the ABS module is not sending that pressure and it is causing the code to pop up. I would need to look at the code sheets I have and see what the relationship is between the two codes (P1637 and C1440).
he mentioned earlier using a dissimilar sized spare wheel.
would that not mess up everything and cause all these issues?
i suggested this in his other post
iownme, if there was a different size tire (lets go extreme here and say he only put on a 10" diameter wheel-not really possible, but just because). This would cause the one wheel to spin tons faster than the other wheels (assuming DSC did not kick in or ABS). The ABS module would still see an input from the sensor. This erroneous signal would cause the speedo to indicate faster than the car is actually moving (this would be due to the ABS module seeing 3 wheels spinning at 30 mph and that really small wheel turning at what it would equate to 100 mph, averaging out to around 50 mph). But, the computer would be getting all the inputs it is looking for. The loss of the speedo (the ---- on the instrument cluster) is saying that the instrument cluster is not seeing any data for the car's speed. This would have to happen either inside the ABS module, the wiring connecting the two modules, or the ECM.
So, in short, a different size tire on the X-Type is bad because of the AWD system and can lead to failures in the drivetrain and the ABS/DSC acting really funny because it would see the one "slipping", but that would be a physical problem, not a computer problem like the CAN Bus error is saying.
Hi Ronks2,
Did you check those CAN bus wires? All those codes you are getting point to CAN bus problems.
As per workshop manual:
C1440: "Brake pressure signal fault. Brake pressure sensor failure Control module failure. Use the Jaguar approved diagnostic system to measure the brake pressure signals"
U2509: "ECM unable to fulfill DSC CAN torque reduction request. Verify integrity of engine management system CAN network fault. For ABS/DSC CAN network tests, GO to Pinpoint Test G"
P1637: "CAN ECM to ABS/TCCM or DSC control module network malfunction.
Module power supply or ground interruption CAN open circuit fault; ABS/TCCM or DSC to ECM CAN short circuit fault ABS/TCCM or DSC module failure. ECM failure Refer to power and ground test for suspect module. For ABS/TCCM or DSC CAN circuit tests,
GO to Pinpoint Test C. Please check part is not on any form of prior authorisation before replacement."
U2509 and P1637 pinpoint tests are on section 418 "Electrical Distribution" / "418-00: Module Communications Network" on Workshop manual, starting page 2200
There is no separate pinpoint test on workshop manual for pressure sensor signal fault. Sensor itself is not an expensive part, but I'd not replace it until CAN is functioning properly. It probably is ok, after CAN works again.
You can try to download workshop manual from the stickies -section, or try googleing for it. Or install JTIS.
-I tried to upload WSM pages, that have those pinpoint tests, should be attached..
When I had C1440 and P1637 codes on my early 2004 MY 2.5 AWD, I remember first changing the pressure sensor, and that cured C1440 but P1637 remained.
After testing CAN wires, it was clear that problem was on the ABS module. I had it repaired, but it failed again after just two years, this time with different codes (can't remember what anymore).
Luckily, back then, while the original ABS module was been repaired, I had opportunity to purchase second hand ABS unit from an earlier model (2002) with DSC, that was tested good. And I did, just incase my original unit would prove to be unrepairable. So when my unit failed again recently, I swapped it for the spare unit I had.. I got the info from here, that one member had done similar swap, with those same unit model numbers that I had (original and spare from 2002MY) so I was confident it would work. I've been driving few hundred km since, with out issues.
When I had this problem, I discussed with local Jaguar and Land Rover shop (independent) for possibility to reprogram ABS control module from later model car, and they said it could be done.
But if you have DCS, then you need module from car that had it too.
Hope this helps!
Ok, doing some looking in the various manuals I have, the C1440 code is caused by either a bad pressure sensor or a failure of the ABS module. This would play into the CAN bus being bad as other computers are not able to get the pressure reading from the sensor. So, this pushes me back towards either a bad ABS module or the CAN bus wiring associated with the ABS module is toast. Because we are not getting a C1288 code (failure in the pressure circuit itself), this is telling me that the problem with the pressure sensor is a secondary indication, not a primary (ie, caused by something else, not the problem itself).
Will a pressure sensor from a non DSC car work on mine with DCS?
I have a quick question on the CANBUS wires. Do they run from the ABS to the ECM and then out and on through the rest of the car? Are they all Green Y and Green Br?
I will start again by looking at the wires between the ABS and the ECM first. IF that is clear should I continue on to the OBDII port?
Will a 20006 ABS module without DCS, work in a 2006 with DCS? What earlier year X-type ABS will work in my 2006 X-type?
The junk yards that have parts are here in South Florida, so I am trying to buy parts and fly up to NH where the car is to fix it.
I have printed everything we have done here so I can make a check list.
RONKS, I will need to check my drawings again, but I do not believe non-DSC cars have the pressure sensor. That was something just for the DSC system. I am going from memory here.
As for the with(out) DSC question, the 2 units are different and have different plugs. So, I do not think you are going to be able to just unplug one and plug in the other. Not to mention that some modules would need to be reprogrammed so they are not looking for signals that they think should be created by the DSC module.
RONKS, well, that will teach me for going from memory. It would appear that all 3 modules for the ABS system (basic ABS, traction control version, and then the DSC version) all seem to use the same plug and from what I could tell, the same pin out. Now, obviously, the DSC version has more wires for the various inputs, but the core of the unit is wired the same. So, you may be able to take a basic ABS module and plug it in to test things. But, as I did remember correctly, the pressure switch is only installed in the DSC version. The other 2 do not have a pressure switch in their diagrams.
I was able to hit the junkyard yesterday. The two cars that were there, did not have DSC, and you are right there isn't a switch on the side.
I hope that a DSC car shows up before I get back on a plane to work on the car at the end of the month.
I am wondering if the DSC was an option starting in 2006 as all of the 2005 and down cars haven't been equipped,
Would an ABS unit with DSC from an S-type work on the X-type?
I was able to hit the junkyard yesterday. The two cars that were there, did not have DSC, and you are right there isn't a switch on the side.
I hope that a DSC car shows up before I get back on a plane to work on the car at the end of the month.
I am wondering if the DSC was an option starting in 2006 as all of the 2005 and down cars haven't been equipped,
Would an ABS unit with DSC from an S-type work on the X-type?
RONKS, DSC is one of those options that has always been available on the X-Type (even back to 2002). The 2002 and 2003 cars the DSC really wasn't needed as the viscous coupled transfer case pretty much did the job of the DSC. So, while the car could be optioned with DSC, most people did not get it. Starting in April 2004, Jaguar changed the transfer case and went with an open differential style transfer case. So, while power does get transferred to all 4 wheels, when 1 wheel looses traction, it takes all the power and can leave the car stranded. It took jaguar until 2006 to make DSC pretty much standard on any AWD X-Type. Not every AWD car has DSC starting in 2006, but you are running a very high percentage (something like 95+%) that will have it.
As for the S-Type and X-Type DSCs being transferrable, I would look at the part number, if the middle part is the same, then it should work. But, I have a feeling you are going to find it is a different number and therefore mean that they are not compatible.
Hey Guys. I made it out to the boneyard the other day to hit that 2007 Jaguar. , It had the DSC switch, but didn't have the control valve on the ABS to control it. It also had the brake lines in the straight row on top.
I have a 2006 with every option available at the time EXCEPT DSC. Mine even has the 5 speed automatic transmission WITH OVERDRIVE (listed right on the window sticker). Idk why with all the options the original owner bypassed that option.
Last edited by Dell Gailey; Feb 12, 2026 at 12:25 AM.
I was looking into how to disable the red gear box and stuck in 4th limp mode. I came across a bulletin that stated if you hold down the DSC button for 10-15 seconds it would disable it. I am not near the car this week to try it, so I figured I would toss it out before I forgot about it.
