Fault Code

[Simont485]

Hi All

Fault COde ff44 appeared today on my 6.0litre V12. It is for the A bank hot air oxygen sensor.

Where are the connections in the engine bay. They are really easy to find on my XJ12 but not in the same place on the XJS!!

[PaulGover]

I think it can vary if anyone's ever done work on the exhaust.

If it's the same as my 5.3 V12, you're looking for a long black plastic connector, about the length of a cigarette, but a bit larger in diameter with boss at the end. Mine were cable-tied to the chromed drain tubes running down the top of the chassis moulding behind the flitch plate and in front of the exhaust arrangements. They have three wires inside. FWIW, there's a similar sized connector, but red, on the LHS used to change the ignition mapping for low octane fuel.

[Simont485]

I had to disconnect the battery to charge it. Re-connected and fault code now gone! So is there still a problem? Car runs fine nod code has not reappeared!!

[PaulGover]

The only way to clear engine codes is to disconnect the battery; otherwise they get displayed when you first turn the ignition on. If they don't return after disconnecting, it means they have not been triggered again. That's quite common; the electronics do an awful lot of testing, and sporadic events outside the norm seem to be part of life's rich tapestry.

For comparison, I had a brake code come uponce , but it's never reappeared. That said, I get a lot of FF44 (RH oxygen sensor out of line) events; it's either an exhaust leak, a bad sensor, or duff wiring.

[ptjs1]

As Paul has mentioned, the code will still be in memory until cleared by a scan tool or by losing the voltage on the ecu by a battery disconnect.

A number of Jaguar systems run on a "3 times valid" protocol. In other words, after triggering the fault, if the car doesn't see it on the next 3 resets of the ignition, it removes the fault / error light but stores it in memory.

I would suggest that you clear the code and then wait to see if it returns.

Good luck

Paul