They cleared error code p1b40 from the vcu but the check HV battery kept popping up and clearing intermittently on the way back (it would pop up then self clear seconds later)
Drove it this evening and it went into turtle trying to pull onto a roundabout (thankfully not busy), had to limp it along a bus lane until I could pull over had to power down a few mins to clear turtle.

Will call the garage tommrow, hope can sort something with a more local mg dealer or they’ll come pick it up as the one I bought it from is 100miles away.
I don’t seem to get much luck with mg cars had a 3 a while ago with a dodgy gearbox.

Edit: Remove line spacing (sorry phone did that)

 

Have EXACTLY the same problem with my MG5 with 500 miles on the clock. Been in MG dealers for 9 days now, anf fault still not identified!

 

Deleyed as forum posted twice!

 

The dealer I bought it from arranged for a more local dealer to take a look, they tried to check/update the software and decided it needs a new VCU (Vehicle control unit, essentially what used to be called the ECU). So it's supposed to be going in tomorrow for that.

Mods can remove this if they don't like links to other forums but there's a handful of people now having this issue - Mystery Faults , Red 'Check HV Battery'

 

So I've had the VCU replaced and that supposedly will fix the going into turtle mode, the red check HV battery warning is still appearing although the garage that worked on my car did tell me that it needs a software update to fix that's currently in development.

Apparently the warning appearing is now a known issue and I should be called once the update is available.

What happens next will depend if they did actually manage to fix the going into turtle mode or not.

Edit: Nope didn't fix the turtle mode

 

Same boat here , keep us informed

 

My wife and are going back to the dealer today to pick up her MG5. She has been having the same issues with the ‘Check HV battery’ warning popping up then going away, apart from the last time when the car went into turtle mode in the outside lane of the motorway.
She managed to get it going again after getting to the hard shoulder, she drove it straight to the dealer. They have had it for a week with ‘no fault found’.
When it went in the technician cleared the error log because they were “old faults”, she has only had the car since September.
I'm with you, I’m very unhappy about her driving around a car that at any moment could lose all power.

 

I have been in touch with BBC Watchdog re this problem , suggest you all do the same , maybe if enough of us email them we can get some reputational leverage from the BBC.

 

Mine had the software update a couple days ago, haven't seen the Check HV battery warning since but equally haven't done enough miles in it to be 100% confident it's fixed.

The Dealer needs to raise a case on their Service Now (SNOW) system to MG HQ who should then guide them through what they need to do and make the software available for your car.

 

My wife got her MG5 back yesterday, the dealer has apparently applied a new firmware that’s for ‘HV battery management’ according to the dealer this is brand new firmware that MGHQ haven’t yet released to all dealers.
so far so good, no messages. I’ll update if this changes.

 

My wife got her MG5 back yesterday, the dealer has apparently applied a new firmware that’s for ‘HV battery management’ according to the dealer this is brand new firmware that MGHQ haven’t yet released to all dealers.
so far so good, no messages. I’ll update if this changes.

Currently I believe it's a patch specifically for this issue that has to provided by MG on a case by case basis hence the need for the dealer to open a tech case with MG HQ.