Thanks much for the ending!
I had thought O2 sensor from the beginning BUT found all the conflicting info that you did.

Now the strangest thing is you posted that the car will throw the exact same code for 2 completely different reasons! That I have never seen.
.
.
.

 

Just wondering out loud; could there be a difference here between the EU and the US version? My XJR is US version.

Jeroen

 

No difference. I posted earlier in this thread extracts for year 2001 ON for OBD2 codes (US) and for EOBD codes (EU). I have attached here all Jaguar code related documents that I have.

 

Interestingly, my 01 threw a 1646 when I bought it. Diagnosed a front right side O2 sensor, replaced it and the code persisted until I found this same info about the later AJ27 cars as is in this thread. Pulled both fuel pump relays, shunted the appropriate pins to run the pumps and verified they both were operating and then replaced the relays, code vanished and has not reappeared since, this was about 35,000 miles ago.

 

many thanks for posting all those documents, much appreciated!

Jeroen