I have a 2020 Defender with P400 engine and 88,000 miles. I recently got a "gearbox fault detected" warning pop up. The code is P07B9-11 - which my Autel reads as "Transmission park position sensor B - circuit low - Circuit short to ground". When I press 'P' on the gear selector to go to park, the car goes into park, but the instrument cluster doesn't display any gear. It doesn't seem to recognize that it has gone into park. It will then not let me change the gear at all. To select a gear after pressing 'P' I have to turn the car off, press the start button without the brake pressed, then it knows it's in park again until I pick drive or reverse, at which point the fault come straight back again.

I have booked it into the dealership for this Friday. I don't know if there is possibly a loose ground wire that only affect Park or if the gear selector/module is faulty.

Has anyone else had this fault?

 

This code/error resulted in needing a new valve body for the transmission. They hadn't seen this issue before and I haven't found any examples of this ZF8 failure online either. This was $7560.10.

 

Far out! That is not a small repair bill. As for the transmission oil - I believe it needs 8.5l - looks like you been charged for 10l. (unless there is some different unit 'measurement' in the US).
That said, the specified oil for ZF gearbox transmission (being Shell or ZF) you will probably find cost about $30-33 per litre. You are looking at $280 worth of oil, or even for the alleged 10l they charged you, cost them no more than $330.
Looking at the cost of a new valve vs a reconditioned, if it happens to me, I'd happily save circa $3k for a reconditioned one at anywhere from $600.
Cannot comment on the labour involved as they probably would have thrown in the diagnostic & reprogramming fees in there as well.

 

Ouch. Sorry to hear that.

That's quite the bill.

The part is also available as reconditioned if that's of interest for about half that.

The oil and transmission pan are available from a number of vendors at a fraction of that cost. Essentially buy with the ZF part numbers rather than LR and you save a packet for the same OEM parts.

Case in point. Same ATF is $15/liter. Amazon also have it.

I wonder is there much labor needed, once you have the pan off, to remove the old valve body, and whack in a new one. Seems like it's on the underbelly of the transmission. I'm looking at doing a preemptive transmission drain and fill in the next year or so. Not sure I want to wait till 105k miles.

 

Ouch! Sorry to hear that. As other point out the mark ups that dealers put on parts are really getting ridiculous...

 

I feel your pain. My 2020 has been in the dealership now for three months with a gear box fault. Initially they thought it was a gear selector which was replaced but the fault returned in four days. Then onto the transfer case where a double flush returned the truck to service for two days. Truck has 50k miles so I reached out for help and had a customer case opened. Land Rover was good and they replaced the transfer case under warranty. Truck ran for 24 hours. Now we are on to the transmission and I have been told it needs a new one, however it has been stuck in limbo due to the cyber attack and no one can investigate to approve until their tools are up and running

I too have been unable to find any references to the ZF transmission failing. These are normally rock solid so would be surprised if there was a systemic issue.

Codes for me are:
P0501-64, P174E-62