Welcome to my puzzle. I have been trying to solve it for years now and it's got to a point where I've bit the bullet and asking for some help which I should have done some time ago but held on to the belief I may be able to crack it myself.

After spending many, many days during my recent lifetime sifting through the world wide web I have not found any one who has documented having this issue hence I felt the need to immortalise my troubles on these here pages of wisdom.

I recall first coming across this issue when in Paris 3 years ago but at that time the occurrence was very rare. I was wishfully hoping doing all the 10 year/100,000 mile fluid changes would make it go away but it just got gradually worse.

Fast forward to present day and it is now a constant issue, I dread to do any journeys as it is inevitable the auto gearbox will fail:

When the RR is cold all is fine, could drive to the moon and back (if it could) and the gearbox will work perfectly. However once the car has warmed up if the ignition is switched off upon restart all the Xmas lights twinkle on the dash, Transmission Failure, HDC Fault System Not Available, Park Break Auto Release Unavailable, Special Programs Off, Suspension Lowered etc. The gearbox in auto mode starts in 2nd Gear and will only change up erratically when very high revs are reached, holding on to gears for what seems like an eternity and will down shift at the merest drop in revs. However in sport/manual/commandshift mode you can drive it shifting up and down gears manually smoothly.

Previously switching it on and off would make it all go away but it started needing more and more attempts. Now it just stays in fault mode until cooled off after being parked up. I can see a pattern where the longer i've driven the car the more likely the fault will not clear upon cycling the ignition.

All is well if I continue driving in manual Commandshift albeit the auto gear changes have gone in to the Thatcher era. Switching ignition off and on again may eventually clear the fault but can take over half an hour of driving and many tries.

Delphi and Snap On systems show P0915 Gearshift Position - Circuit Range Performance.

My initial thought was it could be the gearshift selector/neutral sensor/inhibitor switch but that's just me relieving myself in the dark. Reading of other people's similar issues highlights one significant difference, their cars won't start as the switch can not determine what position the gear selector is in. Mine starts and drives fine in manual mode so that has me stumped. I would gladly appreciate anyone with any knowledge to bestow some of it on me please and drag me in to the light!  Bmw E36 328i M Sport Cabriolet
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have you tried lubing the selector cable. These can stick and cause the position sensor to give an incorrect reading.

worth a try. - http://www.fullfatrr.com/wiki/TDV8_Gearbox...s_of_drive

possibly one for RRPhil.

the Christmas tree lights, are possibly another and sound more electrical than mechanical. There is a plethora of things which can cause the dash to light up, from dodgy terminals on the battery or poor alternator voltage, to ABS sensors.

Are you getting a decent voltage on when the car is running. The Alternators in the SC are less friable than in the TDV8 but are in the end probably still a denso unit. There is nothing that can't be fixed with a hammer😜😜
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Thanks mate for the lightning fast response, any possible solutions will be acted upon! I'll take it to my mates place and we'll give it a go

The error lights are defo to do with the gear selector issue imho, whether it is the cable or a sensor is another thing. The usual culprits have all been replaced over time, new battery, alternator, starter motor and bulbs among other things to rule out any of the funny gremlin triggers. Bmw E36 328i M Sport Cabriolet
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My vote is for: "inhibitor switch" .
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Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Thanks Joe90 for taking part I had pinned my hopes on that for quite some time, so much so that I took it to mates to have at it but he persuaded me it can't be that as in that scenario the car wouldn't start.... Bmw E36 328i M Sport Cabriolet
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It’s not easy to speculatively troubleshoot issues with the Mechatronic unit, but fortunately it is easy to remove it and get it tested. I haven’t heard of it happening before, but could the transmission fluid temperature sensor possibly have failed, and it’s putting the transmission into a different shift mode when it gets hot? Solenoid problems are so common on early 6HP26s that it makes sense to eliminate these, and other Mechatronic issues, first from your enquiries before - if necessary - moving on to less likely causes. If your transmission works fine in manual mode, then it seems unlikely that you have a mechanical running gear problem and hence the issue is more likely to be control related (electronic/electrical/hydraulic).

Phil

Thanks Phil, always a privilege to hear (read) your wise words and honoured you have time in your busy schedule to respond to philistines like me

I'm actually from Blackburn but my parents moved to Leicester when I was young. Still visit the old stomping ground when family occasions dictate

My mate did mention he recently came across a merc with the same issue and it was the mechatronic, if you know of any specialists in the midlands who could work their magic on the old 'box I may just give it to them if it gets the problem gone once and for all. Alternatively will strip it down and send to the same place that done the merc one and see how it goes.  Bmw E36 328i M Sport Cabriolet
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