Hello beautiful people with jaguars. My names andreus, and I recently ran into a beautiful 99 XJR with 103k miles. It was kept in a rural spot so clearing the codes wasn't essential. Fortunately it has just one. Unfortunately for me, it's a pretty extensive code. Could be an actual fault, or it could be electrical from what I've gathered. I bought a Chinese mongoose but unfortunately, I had very little success actually connecting to the car. I cleaned all the grounds and charged the battery (came with a battery charger, guy had a collection) but to no success. I took it to a local specialist and they said they believe it's the Jgate, and want more money to further diagnose, but not fix. Would resetting the ECU get me closer? Or do you think that they're right? Unfortunately, they don't talk with enough confidence to reassure me that they're doing a good job. The car is also throwing an ABS and traction control light, but it's not essential right now. Right now i want it registered and on the road, bare minimum.

This is what i found as far as what to do inside IDS/SDD. Seems like this is what they want you to do, but this isnt close to what the specialist recommended.

 

Here's some extra information I pulled on this specific code.

If there WAS something to go wrong, i had assumed it was the dual linear switch, and not the Jgate.

The electrical diagram for the dual linear switch

 

Knowing where the fault is coming from is a good start. Determining the actual cause is
a rather daunting task. Wiring faults can be very tricky and Jgates are difficult to diagnose.
I would definitely check the dual linear.

 

Will do will do. I grew up knowing that the electrical in these British cars were a nightmare so I thought maybe the specialist had maybe seen it before. Will bust out the old volt meter and get to workin.

 

The Merc box in the XJR is known to leak fluid into the connector where the loom attaches to the box. Seems a good place to start as I believe you can unplug it from outside the box & check. If it's wet with fluid then clean it out & see if that fixes the code. You'll need to sort the leak but it'd prove what it is.

 

All super sound advice. Will do some investigative work.

 

Info on the leak.

 

oil can wick up the harness into the tcm. i’ve done sprinters where the TCM is literally overflowing.

1601 is a checksum error, the dual linear is just a range sensor and usually throws a 0705 when it kicks the bucket. you can even test it by just unplugging.

or just replace the TCM, takes 5 minutes tops and super low failure item. fire the parts cannon and ebay return if it doesn’t work out.

 

No leak, and clearing the codes fixed it i guess. I do have some new codes relating to the map senor and some low input codes. So technically the problem originally mentioned was resolved through clearing the codes. P0171 and P0174 ( relates to lean mixture in banks 1 and 2) I'm assuming it's a MAP sensor but I'll figure it out. Thank you guys for the help! And the dual linear switch works beautifully

 

the map sensor is only for egr performance monitoring it isn’t used for mixture control. you’re looking for maf issues or vac leaks

 

Clean the MAF sensor (I use CRC's MAF sensor cleaner, but any electrical cleaner works); remove the air hose from air filter box to throttle, check for cracks; clean throttle bore and plate (CRC makes a cleaner for that too); reinstall and tighten all fittings; clear codes and drive it. Run a can of fuel system cleaner (Gamout's SeaFoam look alike, SeaFoam, Lucas' best, Techtronik, all good enough); tighten (gently) nuts on cam cover; check o-ring on dipstick (light vaseline); reset OBD, drive it. If those simple things fail, you need to check for leaks with a smoke device or butane torch (just gas, no flame) -- lots of threads.

But you have air leaks . . .

 

I'll grab some cleaner tonight and get on it. I also believe the water pump decided to give out. Anyone have a belt diagram for a 99 XJR ? There's also a very small leak from one of the plastic connectors on the coolant reservoir. Any places in the US/WEST that sell these little guys? Cheers

 

I had a 2003 XJR for a while that had numerous transmission warning codes and sometimes would need to put it in neutral to start the car. Turns out the cable from the shifter to the transmission was a bit out of adjustment. Once I adjusted it, under the center console shifter linkage area, all the codes went away. Not sure if that is what is wrong with your car, just throwing it out there. Hope you get it sorted soon!