Decided to fire up the cabin heater via the app yesterday; something I don’t do very often. Given that I have the P400e I have the choice of heating using the battery or the engine (no FBH AFAIK). I went with engine, running it for about 10 minutes.

When I got into the car it was toasty warm, but when I put it in D it coughed and spluttered for about 2 meters then threw up a ‘gearbox fault detected’ message on the dash. 2-3 on and offs / lock and unlocks and the same message. Plenty of revs but no forward or backward drive.

After about 30 min on the blower to the breakdown services, the old girl fired up, went into gear, and got me home no problem!

Any ideas what it could be?
Could it be that running cabin heating with the engine running somehow run’s the 12v batteries down? 2018 P400e AB LWB

Gearboxes are often the most susceptible to voltage drops. Is it possible that when sitting at idle its not been topping up the battery well enough, and the voltage dropped at some point making it throw a wobbly. V8 or else ...

Sounds to me like voltage drop as a result of the FBH running. The gearbox ECU may have needed a few minutes of engine running to raise the voltage sufficiently to boot properly. 2015 Range Rover Autobiography 4.4 SDV8

I dont have the FBH. The app starts the main engine which i assumed means the alternator she be preventing battery drain? 2018 P400e AB LWB

Took the car into my local main dealer today. They say they can’t find any trace of a fault, but also say they have no time to check the battery health. 2018 P400e AB LWB

Test it yourself? See this thread for the gadget you need, appreciate searching “Battery” on here brings up 472 results:

https://www.fullfatrr.com/forum/topic65160...ery+tester

 “If it ain’t broke, don’t fix it” -where’s the fun in that?

Main battery is showing full health, auxiliary is showing SoH of 57%. Both are original Land Rover parts so I can only assume the previous owner replaced the main but not the auxiliary.

I guess that’ll be the culprit for my gearbox fault then? 2018 P400e AB LWB

I wouldn’t have thought the Aux battery could affect the gearbox at all, it’s only to augment the Stop-Start system. Spurious errors start to appear only if the whole system voltage drops below a certain level, so normally in such instances, the main battery is involved. The next step would be to run a full diagnostic check to find out which DTC’s are thrown up, and take it from there. “If it ain’t broke, don’t fix it” -where’s the fun in that?

Main dealer claims they couldn’t replicate the fault and there were no DTCs. Given that this only happened last Thursday evening and it appeared three times in a row; ignition on ignition off, I’m a bit skeptical frankly. He said that sometimes it overwrites faults or it resets, something along those lines.

I guess I’ll be ordering the Autel OBD reader asap 2018 P400e AB LWB

Unlikely on a MY2018 car I know, but the body earths under both forward front wheelarch liners are a common issue leading to electrical er, Gremlins

Anyway, a free DIY job, and a good bit of preventive maintenance with some Lanoguard grease or similar is a good idea, even if they are OK right now. “If it ain’t broke, don’t fix it” -where’s the fun in that?

Thanks Gremlin; a job for a sunny summer’s day.

I’ll report back when I can read the fault codes. In the mean time the car has been as good as gold, but there’s a battery booster in the boot just in case.

The dealer also told me it’s unlikely to be the battery since the car would give me a warning. Well early on in my ownership I had the doors and boot open for a fair while then it wouldn’t start or even attempt to turn over. No battery warning at all but after a few hours on the ctek all was well, so I’m not sure I can rely on there being a warning. 2018 P400e AB LWB

My Tesla trickle charges the 12v from the 100kw battery. I’d probably incorrectly assumed the RR would do the same since it’s a plug in hybrid 2018 P400e AB LWB

Autel ordered and received but unable to decode my VIN. Waiting for a fix from them. 2018 P400e AB LWB