A potential buyer took the car on a test drive yesterday and quickly came back saying the ride was incredibly harsh. I subsequently drove the car and he was correct....it felt like the time I had forgotten to reconnect the accelerometer located behind the fuel tank (in the boot) after changing out the fuel pumps. (it was/is plugged in). So now I'm scratching my head as to where to look for a solution. The harsh ride remains whether the Sport switch is ON or OFF. The red light on the switch works, but doesn't alter the harshness from the suspension..

Background: I had run the car through an automated car wash the previous day, and also replaced the rear sway bar links (with the rear suspension in a partial droop position). I'll reset the links with the suspension at normal ride height, but don't think it will impact the CATS....it probably just gives a very small upward push at the rear (and screwed up the rubber in the links). So I think that leaves a disconnect/malfunction at one of the shocks, water intrusion at an electrical connection from that automated wash, or a disconnect at an accelerometer.

Question: I've read something about three (3) accelerometers. I know about the one in the boot. Where are the other two? Or is there only one for a 2002 XJR?

Ideas/recommendations? Thanks

 

Well from what I remember in the handbook it's solely accelerometers that govern the CATs system, it's nothing to do with sports mode. So that's one thing to tick off the list.

 

The SPORT MODE switch is only for the GEARBOX, it has nothing to do with suspension.

 

I was just in the garage, and think I found the culprit. The driver side URO front shock donut from Rock Auto, which might have 1500 miles on it disintegrated...likely sending the system to the default mode. I just ordered the ones from forum member phobman. Thank goodness the original Jaguar spec rear isolators/mounts were still available from the Jaguar supply houses when I replaced everything.

Thanks for setting me straight on the CATS function/input. I still wonder where the other two accelerometers are located (if there are in fact more than the one in the trunk....)

 

The electrical guide will have the locations of the suspension sensors and other components.
Also the introduction to the X308 sedan and update student guides cover the suspension details.
Gus should have all that on his site?

 

Thanks, Bob. Found the diagram....front vertical and lateral accelerometers are on the left front strut tower, rear vertical accelerometer is on-center behind the large forward upholstery panel in the boot.

 

I've just installed new foam cushions for the front upper shock mounts to see if the disintegrating ones might have upset the CATS brain. No change...the shocks are obviously at full "firm" at all times....no warning light on the instrument panel. When I got back from a test drive this morning, I pulled the electrical plug from the front left front CATS shock and checked that the suspension fault light illuminated on the instrument panel....then plugged the wire back into the CATS shock and the panel light went out. Same procedure for the right front shock...same result. I did not check the rear plugs as they are not very accessible. (I did replace all of the rear suspension donuts and shock bushings about 500 miles ago and the shocks looked like new). I was meticulous about reattaching those rear plugs, and since the light on the instrument panel is OFF, it would seem that a disconnected rear plug would be showing up as a fault on the instrument panel (same as for the front).

By the way I disconnected the battery ground overnight and the issue persists after reconnecting and short test drive. I have not done the hard ground exercise yet, but suspect it won't erase the hidden "firm" setting in the computer. I guess that's next before I take it to the dealer or a shop that has a code detector that is more sophisticated than my engine/transmission reader.

Any recommendations as to what to do next?

 

Fault memory can be read from cats if my menory serves right. But I'd start from basics. Are all shocks electrical resistances same? Same between fronts and same between rears in case rhere is differences between front and rear.

 

Thanks. I'll check resistance at the front....as you no doubt know, access at the rear is problematic.

 

You can get the resistance info from the control module without probing the rear dampers themselves.

ADAPTIVE DAMPING CONTROL MODULE EM68 / 35-WAY AMP JUNIOR POWER TIMER / BLACK ADJACENT TO PASSENGER SIDE BLOWER /
GLOVE BOX ASSEMBLY

 

Excellent pointer, Bob. I'll search for the box and check it out. If those values look OK and the rough ride persists, I wonder if you have the test equipment to check for errant, stored codes? I could drive it up there most any time....

 

I have both WDS and IDS like I used at the dealer in Fort Worth.(both are old Ford units with Jaguar software installed)

 

I'll PM you when I get the resistance numbers...probably a few days. Thanks.

 

@ MOTORCARMAN

Bob, I removed the glovebox for access to control boxes. There are two....one on the left (transmission hump), and one on the right (next to the fender) with a snag of yellow and orange wires. I presume it's the one on the right, although the black box has labeling suggesting it's related to anti-lock braking...maybe both?

Anyway, it looks to be difficult to get meter probes into the space. Looks like one securing screw at the bottom of the module, but I hesitate to attempt removal for fear I might never get it back in position... Do I have the correct module, and in your experience can I move it for access?

Left box
[img alt="Left box on transmission hump

"]https://cimg4.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/2000x1504/004_fa85c99a872e4af17fc4d9c5593ed7e7fb3a43fe.jpg[/img]
Left box on transmission hump


Module next to fender

 

Never had to access the module.
I don't know if DATALOGGER will work for 'reading' each damper but I would try that?

 

OK, I'll make an attempt to get readings via a meter/probes today. Any danger of damaging the modules by sticking probes in the wire sockets (power off)...or do I have to pull the wires out of the module?

 

I don't think reading resistance will affect anything in the module.
The only thing we were cautioned against was the AIRBAG resistance with a meter.
We were to use WDS/IDS DATALOGGER to interrogate the module for AIRBAG resistance.

 

Thanks. I found the shop manual diagram showing general connector locations...I think there are two in the trunk if I can find them....possibly better access than the module....

 

Bob, Well after tearing out all the trunk panels looking for a connector, I finally managed to get resistance readings on all four shocks by probing at the module....roughly 8 ohms on all four. So, I guess there's some sort of stored fault in the brains. I wonder if you would be able to hook it up to your diagnostics and possibly clear whatever faults might be causing the problem? BTW, I left a voice message at an old phone number I have for you. Thanks, Eric

 

I got your message. I don't carry my phone sometimes.(I leave it on my desk)
Let me know if you want to come to the shop sometime for a diagnostic session.
I work on cars sometimes for a few hours, other times I have farm/ranch things to do.(I can't hear the phone when I am on the tractor)