2004 XJR VDP I had abs/dsc fault with trans in limp home. Scan tool code showed RR abs sensor. changed sensor no fault for about 40 miles. Abs/dsc fault came on but no trans problem. Checked abs system with diagnostic tool. Everything perfect. What should I check next. I plan to change sensors around left to right to make sure it's not new sensor. I also plan to check wheel bearing but only 52,000miles on car. I appreciate any suggestions. Thanks

 

Did you check/clean the reluctor ring while in there?

 

yes, it was tested by turning wheel and checking output. Everything passed perfect. Found nothing out of specs. Thanks for the reply

 

A wheel sensor failure will not cause limp mode.

looks like the fault is intermittent.

https://www.jaguarforums.com/forum/x...minated-90284/

 

Could be an ABS module pin fault, which sends trans into limp mode.

http://www.jagrepair.com/images/TSB/...%20Cluster.pdf

 

Hi preacherbob,

Welcome to the Jaguar Forums! It's great to have you with us.

Could you please post the exact diagnostic trouble code that referred to the right rear wheel speed sensor? There are more than one code for that sensor, and knowing the exact code will help us give you the most accurate replies.

This is true of all the wheel speed sensors except possibly the right rear. If the X350 follows the pattern of earlier saloons, the right rear sensor provides the vehicle speed signal referenced by the Engine Control Module and Transmission Control Module for executing smooth gear shifts, as well as the Variable Assist Power Steering, speedometer, cruise control, and all other systems that rely on an accurate vehicle speed signal. This function of the right rear wheel speed sensor is not very well documented for any of the models: it's usually hidden somewhere in the technical documentation. I took a quick look through a few documents but have not confirmed this yet.

In addition to the potential causes merion1 has already mentioned, another common problem is a broken wire in the sensor harness that causes an intermittent interruption in the signal, triggering the diagnostic fault code (DTC), CEL, and possibly Restricted Performance and/or Limp Home Mode.

One way of tracking down a broken wire is to disconnect the electrical connector from the ABS module and connect an ohmmeter across the terminals for the right rear sensor, which are pins 42 (Brown wire) and 43 (White wire) of the connector. Set the ohmmeter where you can see it from the right rear wheel area, and while watching the reading on the meter, flex the wheel speed sensor wiring harness at various points along its length. If you see the resistance on the meter jump to infinity, overload or OL, you've found the break.

Also, I haven't heard of this on X350s yet, but on the earlier saloons with Ate/Teves ABS systems a common problem has been cold, starved or cracked solder joints on the circuit board in the ABS/DSC module. Lots of info on that topic in the forum.

preacherbob, please visit the https://www.jaguarforums.com/forum/n...-intro-must-5/ and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.

Cheers,

Don

 

Thanks for your reply and the info. The next post by Don B. says the right rear sensor can cause limp mode which seems to fit my experience with this problem.
Thanks again.

 

Thanks very much for your reply. My experience with this problem seems to agree with you about the limp mode. I'm old and forgetful so I didn't copy down the code. The new sensor seemed to fix the problem, but after driving at hwy speeds for about 30 miles the abs fault came back on. I drove back home and had the mechanic read it. RR sensor again. As I left the shop the fault went away. The next day he tested the system with a diagnostic tool and found no problems. I plan to drive it today for about 75 miles. I will update if the fault returns.
Thanks again, you eased my mind about the trans.

 

One thing that may help in the diagnosis: the next time the fault appears, pay attention as to whether your speedometer stops working, possibly very briefly.

Cheers,

Don

 

Thanks again for the suggestions. I drove the car today to Panama City and back, highway and city driving of about 80 miles. No faults! One interesting thing: I have had an intermittent air suspension fault because I changed all the air shocks,(ie kept air suspension system) I had never cleared the codes after the change. The air suspension fault did not come on and neither did the abs fault. I saw somewhere that there is a connection between the two modules but I don't remember what. I believe it was a speed input from abs to air but not sure. The abs fault has only come on that once since I changed the speed sensor. Thanks again.

 

If you loose the connection between the ABS and IP you will get the "Christmas tree" on the IP however the IP will switch from using the ABS for speed to the TCM

This lets you know the fault is the ABS module pin

IF you get the "Christmas tree" and loose the speedo the IC is unable to see both the ABS and TCM. This lets you know the fault is the pin at IP

Follow the TSB on the pin repair.
Of you search this fault I have posted the TSB a few times

Cheers
34by151

 

The Air Suspension Control Module (ASM) receives the same vehicle speed signal as other ECUs, because the suspension is designed to lower 15mm at speeds above 105 mph for reduced drag and better stability.

Cheers,

Don

 

Another good thing to do is upgrade the earths behind the headlamps

The airbox side earth is also the earth for the air compressor
The ABS side is also the abs earth

I added a stainless bolt next to the earth then moved the lugs over to it. I also added a jumper to the original earth for good measure but this is not really needed.

If your earths are playing up it can generate an "Air Suspension Fault" in the message center and an orange MIL. This assumes you have HID headlamps with the LAD5GL (12 pin) ballasts.

The ASM talks to these ballasts via the CAN bus. If the ballasts are not responding (due to an earth issue) you will get the yellow mil and "Air Suspension Fault". You can simulate this by removing the plugs from the back of the headlamps

If you have the ABS pin issue or ABS earth issue I would expect to see the P1799 code come up. You may miss the code as your issue is intermittent

P1799 - CAN network malfunction
Substitute transmission output speed for DSC vehicle speed

This is when the ABS speed signal is lost and the system starts using the trans speed

If you have data issues with the trans you will get the P0720 or P0721 but these are rare

Cheers
34by151

 

Thanks for the info. I have only had the abs fault once since changing the sensor. The air suspension fault has not showed up again either.