Started to get the gearbox fault message intermittently at around 145k km on the clock. Dived into this forum, learnt about XF tranny, 'Sealed for Life', the wisdom of replacing transmission fluid before 150k km, including the pan and filters. Did just that, my cat is approaching 160k km.

So I just wanted to note my appreciation of this forum. Otherwise, it would have been either replacing the tranny or ditching my beloved XJ!

Even after that, the fault code does appear may be once or twice a week, especially navigating through rush hour traffic (Singapore).

I also noted a couple incidents, after washing the engine bay, that I got the Restricted Performance message. This tends to clear after a day or so... I suspect I got some of the electronics wet.

I also noticed that this is followed by an increased occurrence of 'Gearbox Fault'

Couple weeks ago, I decided to do a 'reset (cutting off 12v supply). So far so good, no Gearbox Fault message even going through rush hour traffic on a couple of occasions.

From the above, it seems like the ECU is taking data from MAS, ignition, etc and giving that to the ECU for the XF. 'Bad data' recorded tends to mess up the performance of the tranny.

Can anyone in the know comment or shed some light on my observations?

Cheers!

 

Knowing what the code/codes were a result of the gearbox fault will be helpful in determining if your optimism is warranted. Also, exactly what driving parameters like acceleration, deceleration, which gear, high rpm, low, noises present, cold operation (before reaching operating temp), etc. Details are critical here.

Most of us avoid 'hosing down' the engine for just that reason. Wipe down takes longer, but is safer.

BTW, ZF tyranny, not XF. Specifically ZF6hp26.

 

That's right, ZF. I understand the codes were mainly related to insufficient pressure.

No more hosing down ☺

 

As the box gradually wears, sometimes you need a reflash of the TCM to reset pressures etc. Common symptom is a rough change 1-2, 2-3, sometimes 3-4. Each one has its own fault code.

 

Thanks for the feedback.

How do I go about flashing the TCM? Sounds like a software, but how does it get the latest data to update the pressure thresholds?

Thanks!

 

Nick, that' requires dealer software and hardware, unfortunately.