I have an intermittent electric problem that has baffled my dealer and a good independent mechanic. The symptoms don't seem to correspond exactly to any threads I have been able to find on this forum.

My 04 XJR at random intervals announces that the DSC is not available. Simultaneously, the ride gets very bouncy. When I turn the engine off, even for just a second, the problem disappears, and leaves no error code. I bought the car with about 40k miles on it about 5 years ago, and the problem has been happening pretty much all along. It may be happening a bit more frequently now, but it is so random that it is hard to tell.

I assume the stiff ride is because the shocks are pumped up to full pressure, and maybe that turns the DSC off, but I don't know what the relationship between shocks and DSC is, or what would max the pressure in the shocks. Yaw control maybe requires differential pressure? I did have the front shocks and compressor replaced several years ago. That cured some other problems, but not this one.

Anyway, there can't be very many faults that would cause the symptoms I described: DSC light, stiff ride, instant cure by turning off engine, and no error codes. Someone here must be able to say "oh yeah, that's..."

I would really appreciate some advice.

Thanks
TB

 

Not sure if this fits, but I had a similar issue. In addition, my right wheel sensor would light up. I had the sensor replaced under my extended warranty. No DSC issues in past 8 months per my memory. Might be worth a look.

 

Thanks DAB. I'll take a look at the sensors (if I can find them). When you say "light up", does that mean a dash warning light? I haven't gotten that for any sensors. Also, did you get the harsh ride?

TB

 

I did a search on this because I have the same issue...and it seems that only the dealer can read the chassis codes that most obd2 readers wont. But anyhow it seems to either be related to clogged or dirty speed sensors (which are magnetic and one at each wheel) or a wiring problem with either one of the speed sensors or the front fuse box area. It is suggested to remove each sensor, clean it with electrical contact cleaner, and the connector as well, then clean off the part of the wheel that the sensor is installed to monitor with brake cleaner. I thought I also read for the rear wheels the entire rear end must be jacked up so you can turn the wheels and use the brake cleaner, because the opposite wheel turns the other way and there is limited access at the rear axles... Its also suggested that all the connections to the front fuse box be checked. Also it could be a bad sensor altogether but I would lean more towards wires or cleaning if it works most of the time, as mine only trips out once every 3 months or so

I have not done this myself yet but this may point you in the right direction.

 

I had a similar issue with our first 04 XJ8, it went into Jaguar service 20+ times and you know what it turned out to be: the wiring right under the gear stick for the DSC switch.

Turns out it was causing a short and throwing out berzerk error messages. Jaguar was able to replicate it on a road that I found had bad rutts and it would cause the short. 20 tries and they literally replaced everything in that car...if they would only listen to me in the 1st place...*sigh*

 

Thanks to both of you. That gives me some things to check out. I don't think it is a loose wire, however, because it doesn't seem related to road surface or other driving factors. In fact once it happened immediately after starting the car, before I even put it into gear. But it could be some other initiating factor that then had the same effect.

TB

 

That fact that you dont have codes(if really read by a computer that will read chassis codes, as stated not any old scanner will work)
i dont believe it would be anythhing other than an ecu module issue. Power, ground can network, internal module failure. When have have a fault and that module thinks everything is fine i suspect the module. Crazy people never think theyre crazy
same with communication networks. If all the modules have an issue with 1 and that module does have any codes for coms with others, thats the faulty thing to start with.
Now even if you have a momentary fault in a wheel speed sensor or shock or other area pertaining to abs and dynamic stability control. It will retain a code/codes. Now if it is truely a fault that is "pending" at the time of the fault and you turn off the key it doesnt reappear, because it doesnt see that issue again on restart. This is more difficult if its a code that will set if its a "consecutive trip" code.ie it have to see that fault on 2 back to back key cycles to set. You would have to drive to the dealer and scan while the fault is active without shutting off the key.
When talking about a loose wire/connector. Forget the term loose. Think connected, and tight but poor contact. Many times disconnecting a connector and reconnecting it cleans it and restores a good connection. And since you can access all the connections to the wheel speed sensors. I would disconnect them and reconnect. Past that i would subsitute in a known good module and see if that cures your issue now that as you say it is much more frequent than it used to be

 

Another check point - Check out the battery level - this has happened to my VDP, the battery was not supplying enough current to the electrics which then triggered off a ton of sensor issues including DSC at start up (so I know how you feel when these crappy issues crop up).

Jaguar replaced the battery and then it was fine, no more problems with the errors. When this happened, it was embarrassing as the car was relatively new and I had guests I was going to take for a spin.

 

I have had the same issue Tallbird wrote about for the last five years or so and finally had it fixed. Maybe this will help someone with the same problem;

The issue i had with my 2004 XJR was that at random intervals an orange warning light came on and a "DSC not available" message showed. No big deal but also the air suspension would be pumped up so the ride got quite bouncy. I didn't mind it for the first couple of years. I could clear the problem by turning of the ignition for a few seconds.
The intervals became shorter over the years though and switching of the ignition did not always work anymore. Sometimes I had to drive all day with the light on. So last summer I asked my dealer to have a go at it. He started with replacing the ABS module but that didn't solve it. Nor did a new battery and cleaning the alu ground bolts behind the front headlights. The chassis codes that showed up the most were two specific U-codes pointing to a CAN bus error and the Yaw rate sensor. He eventually found the error in the cabling behind the instrument panel. He replaced the faulty CAN bus cable by a new twisted pair and that was it.

 

I just reread my post #9 and saw I left out the U codes They were U1901 and U2527.

 

Replace/check the battery. Also test the connections. This car needs reliable electric power for all the electronics to work.