Hello, everyone; I seem to have a persistent minor issue. My XJR works perfectly and never throws a code when you leave it in the drive. But sometimes, when you shift from D to 4 from 3 to 4, or from 4 to D, it will throw a restricted performance light. I have tried to read any codes multiple times while the light is present, but it shows no active or pending codes and does not trigger the engine light. Turning the car off and on again will solve the issue every time, and when the light is on, the car shifts normally and runs smoothly but just with restricted power. I think It has something to do with the shifter assembly, as I can get it to trigger to code while driving if I slowly shift from D to 4. It's almost like the switch or whatever tracks the position of the shifter is wearing out, and the computer isn't sure where the shifter is and throws the light.

Something I have noticed is that if you do the slow D to 4, as mentioned above, It won't actually attempt to shift from 5 down to 4. But if you shift with "purpose" quickly, it will always work correctly, and never that I have seen throw an RP light.

Maybe someone with more experience with the J-Gate can point me to what might be going wrong.

 

Has the transmission ever been serviced? Fluid level checked?
Do the easy stuff first but I bet there is a code or two in there.
I think you need to get the car hooked up to a factory SDD system.
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Yes, I forgot to mention that it had a transmission flush and service about 5k miles ago by the previous owner. As for the codes, I agree that there are probably a couple of codes stored that a normal OBDII can't read. What software/computer would I need to get access to those codes? Upon more research, I think that the D-4 switch displayed in the shifter diagram is probably going out.

 

Good to hear about the fluid change! Might still be worth it to at least check the fluid level? It can cause all sorts of things.

Jaguar uses what they call SDD (Symptom Driven Diagnosis). Not released to the public but a number of us on the forum went thru the pain to get an operating system. The software is free and around but difficult to use and zero support since it was never released publically. I finally got a used cheap laptop and run nothing but SDD on it.

Jaguar has now moved on to Pathfinder from SDD.

You could have shift solenoid problems too? Just guessing here.
There is a chance an aftermarket scanner could work but as you know there are tons of scanners out there. We do have some sticky threads about which units to get?
JLR Scanners

IF you want to take a look at that same page I linked above for a long and detailed discussion of the SDD system. It started out as Ford WDS then moved to Jaguar/Ford IDS then to Jaguar SDD. Your older car will need IDS which SDD will tell you when it's connected to the car. Then SDD will load IDS.
You could also just get an earlier version of IDS as some of those were simplier to use than the full blown SDD setup.
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I've had very similiar very minor issue too with my xjr. There is no faults of any kind when driving with D. But rarely when I drive spiritualy and using 2 - 3 - 4 from the J gate with high rpms constantly, I sometimes get restricted preformance. Because this happens so rarely and I don't have ids with me usually it is yet to be seen what gives the issue. All I have to do is to shut down the engie, wait for minute or so and start her again. Then the issue is long gone for a year or so without any codes anywhere. I have not tried to drive in a race track. There It may occure more often.