My 2002 XJR has had the CEL ON for a while. But now it is also sporadically displaying the “Restricted Performance” message. Sometimes the message shows up when I start the engine and drive it slowly out of the garage. After a few minutes or less of normal driving the message goes off, but when I slow down at a stop light it may come back again. Today I drove 90 freeway miles during which time the message never came on, but when I finally got off the freeway and stopped at a light, the message came back. I then drove surface streets and it kept coming back on and off. When I drove it back home -and once on the freeway- the message never came back until I got to surface streets back in Oceanside (home) with, again, similar behavior. What causes this? Is it P1797 (see below)?



Message P1638, which. is causing the CEL, says there is a miscommunication between the ECU and the instrument cluster, which I may have created, myself, when I removed the instrument cluster to replace some bad illumination lights to some instruments. However, if this was the case, why is it OK while driving the car, but it fails when I either stop or slow down? Another code is P1642 (CAN bus failure) and also P1797 (Gearbox fault).

BTW, I’ve been checking this battery (a fairly new battery) on a daily basis and charging it back to make sure it's fully charged.



I see this has been experienced by Pristine97XK8Convertible:

“On my recently acquired 1997 X-308 Daimler LWB (aka Jag VDP), she's recently throwing "Gearbox Fault P1797" yellow warning light during city start stop driving which clears upon an engine restart; on freeway driving, she hasn't so far thrown an P1979”.

I wonder if his "1997 X-308 Daimler" has the Merc tranny that my 2002 XJR has.

 

Only R or SuperV8 models has merc tranny.