2007 Range Rover L322 Supercharged, Transmission: ZF 6HP26

Symptoms: Started as an occasional no crank but always cranked and started after a couple of attempts. Then occurred more often but eventually cranked and started particularly if "Transmission Fault" was cleared with the Gap scanning tool. Now the transmission fault cannot be cleared and starter will not engage (no crank).

Diagnostic Trouble Code: P0850-00, Park/neutral switch input circuit (2B)

My understanding is that the transmission position selector switch is within the Transmission Control Module (TCM) on this make/model vehicle. It appears that the vehicle will not start if the switch doesn't recognize that the transmission is placed in either Park or Neutral.

The instrument cluster correctly indicates the proper transmission selector position. When Park is selected the dash indicates Park, when Neutral is selected the dash indicates Neutral, and same for each position.

This is from the Repair Guide:

The TCM is connected to the starter relay coil. When the selector lever is in PARK or NEUTRAL, the module provides a ground for the coil allowing the starter relay to be energized and allow starter motor operation. If the selector lever is in any other position, the module will not provide the ground preventing starter motor operation.

Hopefully the TCM can be repaired, as a replacement TCM would require reprogramming, which would be difficult to get done. Any ideas on the solution to fixing this issue?

Not sure if the fault codes you're getting rule this out but when I had similar starting problems on mine it turned out to be the linkage from the shifter.

Try putting a bit of pressure forward on the shifter when in P & see if it cranks then. Also give it a shot in N.

I managed to then adjust the linkage and it's been fine since.

Cheers

James

Thanks for the advice. I tried moving the shifter around while attempting to start and found that it sometimes starts in neutral. I readjusted the linkage a number of times but coud not find the sweet spot to consistently cause a start. Unfortunately I'm probably just going to take it to an independent British vehicle specialist. I really like to repair my vehicles myself but I've run out of options and knowledge to get this issue fixed.

This was a very expensive repair as it required a new transmission mechatronic unit, as the Transmission Control Module was the issue. But this item is not available except as part of the mechatronic unit (solinoid mechanism). This also required reprogramming the transmission as the mechatronic unit is specific to that individual vehicle.