Hi all. After several years of ownership my 2005 L322 petrol/gasoline v8 with the stock BMW M62 engine and a ZF 5HP-24 transmission at 139k miles I started seeing trans failsafe regularly after 10-15 miles of driving. The codes are typically correlated with a rough shift into 3rd or 4th and resulting limp home mode.

Wondering if any of you good folks have some guidance on where I should start to address this. Thanks in advance!

Fault codes are:

Shift Solenoid 2 fault (always)
Gear switch fault (infrequent)
Plausibility Fault - Transmission Range Sensor Circuit Malfunction (PRNDL input)

Additional info:

Bosch and Siemens units live data did not match with the (if I recall) the downstream Siemens transfer box module showing the shifter position as invalid when traveling in D after the trans fault. Can confirm.

Last edited by hundel on 13th Sep 2025 7:09pm. Edited 1 time in total

It would make sense to eliminate the inhibitor (or gear position) switch from your enquiries before delving deeper into the transmission itself. Do you have the actual P codes for the faults, or are you using a generic (none Land Rover specific) diagnostic tool? The code that you’re looking for is P0705.

If the inhibitor switch is faulty, the controller doesn’t know what mode the driver wants the transmission to be in, so it defaults to failsafe i.e. locks the transmission in 4th gear. The switch is mounted outside of the transmission, so it’s possible to repair it without pulling the transmission apart.

Another sign that it is this switch at fault would be the selected gear position disappearing from the dashboard. Is ‘D’ definitely lit up when the transmission goes into failsafe?

Phil

Very helpful RRPhil as usual. Thank you for your contributions to the site and for your reply here.

I have an inexpensive multi-vehicle iCarsoft 2.0 with their LandRover software. Obviously incomplete but I should be able to retrieve the raw value behind the gear selector position fault (infrequent) to verify P0705 as well as the numeric value behind the very frequent shift solenoid B (presumably P0758) codes as you advise. I’m also able to read a few dozen Siemens and Bosch scalar data values (pressures, selected gear, etc) during the fault if that’s useful going forward.

The instrument cluster gear select indicator does indeed show “D” while in failsafe after my reproducible solenoid B fault code. Will confirm as it’s possible that’s not always the case (when the inhibitor P0705 code occurs) which would be important.

Assuming all of the above is confirmed (regular P0758 with intermittent P0705), it sounds like a smart approach might be to replace the inhibitor switch, retest, then replace shift solenoid(s) and internal harness. If nothing else I emerge from the first procedure with a little cleaner hands and having spent less on ZF transmission fluid. If I’m getting the P0705 code it will probably be a necessary procedure anyone, and there’s some chance that procedure alone reduces or eliminates the symptom.

Did I get that right?

Exactly the procedure I would recommend

Just to point out that even second-hand inhibitor switches are ridiculously expensive (here in the UK, at least) so I would consider stripping your existing one down and cleaning up the internals to hopefully fix the fault. The main issue is the method you use to hold the switch back together again once re-assembled, to ensure that it remains water-tight. The factory method is rivets.



Phil

I'll take a closer look. I replaced the inhibitor switch 6 years ago and recall they were precious even then. Thanks RRPhil.