MG4 intermittently will not start

[Agrajag]

I'm having a problem with my MG4 51 excite (Australian) where it sometimes refuses to start. I unlock, get in, dashboard lights up with what seems to be every possible warning. It doesn't display a battery SoC (just ---%). I cannot put it in drive or reverse, but neutral/P works. I also cannot turn it off via the Security screen, it says "Function only available in P gear" even though it is in P gear. If I get out/lock and repeat, it just gives all the same errors. When I unlock the car I don't hear the clicking/knocking noises that you normally hear.

The first couple times this happened I called roadside assist and each time, by the time they arrived, I'd go back to the car with them, unlock it, and it would start no problem, which was very frustrating! By this time I had booked it in to get looked at but that was a couple of weeks away. The next time it happened I left the car as-is - warnings on dash, no battery %, didn't lock it - and again, by the time they arrived, there was a battery % showing and the car started no problem! He tested the 12v battery and said it was fine. Luckily I had taken photos/videos so could show them what was happening and that I wasn't making it up!

The car went in for a service and they updated the software. Notes are:

Read DTC found fault in every controle module - delete fault memory - checked battery condition good. Performed software update and configuration in BMS - update all modules as per TAC

That was just over a week ago, and it happened again today . This time we just left it and after about 20-30 minutes it started working again. I've booked it in again to get looked at. It's super frustrating as it's made the kids late for school and we just can't rely on it. My wife has understandably lost all confidence in it and just doesn't want to drive it anywhere (she was stuck far from home today with 2 kids in the car just waiting for it to start working again!)

Has anyone else had this happen and had a resolution? Or can anyone guess as to what the problem might be? We haven't been able to figure out what it is that makes this happen, it seems quite random. At first we thought it might be something like forgetting to lock it, but it's happened a couple of times when we are 100% sure it was locked.

 

[AB71]

I'm having a problem with my MG4 51 excite (Australian) where it sometimes refuses to start. I unlock, get in, dashboard lights up with what seems to be every possible warning. It doesn't display a battery SoC (just ---%). I cannot put it in drive or reverse, but neutral/P works. I also cannot turn it off via the Security screen, it says "Function only available in P gear" even though it is in P gear. If I get out/lock and repeat, it just gives all the same errors. When I unlock the car I don't hear the clicking/knocking noises that you normally hear.

The first couple times this happened I called roadside assist and each time, by the time they arrived, I'd go back to the car with them, unlock it, and it would start no problem, which was very frustrating! By this time I had booked it in to get looked at but that was a couple of weeks away. The next time it happened I left the car as-is - warnings on dash, no battery %, didn't lock it - and again, by the time they arrived, there was a battery % showing and the car started no problem! He tested the 12v battery and said it was fine. Luckily I had taken photos/videos so could show them what was happening and that I wasn't making it up!

The car went in for a service and they updated the software. Notes are:


That was just over a week ago, and it happened again today . This time we just left it and after about 20-30 minutes it started working again. I've booked it in again to get looked at. It's super frustrating as it's made the kids late for school and we just can't rely on it. My wife has understandably lost all confidence in it and just doesn't want to drive it anywhere (she was stuck far from home today with 2 kids in the car just waiting for it to start working again!)

Has anyone else had this happen and had a resolution? Or can anyone guess as to what the problem might be? We haven't been able to figure out what it is that makes this happen, it seems quite random. At first we thought it might be something like forgetting to lock it, but it's happened a couple of times when we are 100% sure it was locked.

It happened to me when I first got my 51 and it was because I wasn’t giving it time to get ready. I would get in and turn the dial but nothing and got messages as you. Eventually I got into habit of sitting and pressing brake then seatbelt then lippy, by which time I could turn the dial to D again or R or wha have you.

 

[Robf]

Do reset the system by firstly holding down the home button until system re-boots (usually about 20 secs). If problem persists then you can disconnect the battery negative terminal (actually undo the -ve connection on the battery) for approx 15 mins and then re-connect. This will re-boot the entire system.

 

[Agrajag]

I wasn’t giving it time to get ready.

I'm going to guess time in your case wasn't 20-30 minutes. Did you get a lot of warnings on the dash? E.g. I get "Autohold fault", "Hill hold currently unavailable", "Airbag fault", "HV Battery Shut Off", "Stability control fault" etc. etc. I get warnings notifications on my phone too.

 

[AB71]

I'm going to guess time in your case wasn't 20-30 minutes. Did you get a lot of warnings on the dash? E.g. I get "Autohold fault", "Hill hold currently unavailable", "Airbag fault", "HV Battery Shut Off", "Stability control fault" etc. etc. I get warnings notifications on my phone too.

No I did not and no it certainly was not 20 mins

Bowing gracefully out of convo

 

[Ian Key]

Might be worth checking the 12v battery terminals are tight.

 

[Agrajag]

Do reset the system by firstly holding down the home button until system re-boots

I have tried that, it just gives the same errors.

disconnect the battery negative terminal (actually undo the -ve connection on the battery) for approx 15 mins and then re-connect

Do you think that might be a "permanent" fix? If I have to do that each time it happens it's not really any different from just leaving it to "fix" itself.

Might be worth checking the 12v battery terminals are tight.

Have tried that, seems fine. I read the voltage with a meter the first time it happened and got 12.4v.

 

[Robf]

I have tried that, it just gives the same errors.

Do you think that might be a "permanent" fix? If I have to do that each time it happens it's not really any different from just leaving it to "fix" itself.


Have tried that, seems fine. I read the voltage with a meter the first time it happened and got 12.4v.

The disconnecting of the -ve terminal of the battery (10mm spanner required) completely re-boots the cars systems, only do this once as if the problem re-occurs, you will need to get back to the dealer as there is a problem with the car that they need to chase down and fix..

 

[Agrajag]

completely re-boots the cars systems, only do this once as if the problem re-occurs, you will need to get back to the dealer

thanks for the info - I think I likely wont do this myself as it's already booked in to go back to them to look at, and I don't want to do anything that will make them turn around and blame me for!

 

[Robf]

thanks for the info - I think I likely wont do this myself as it's already booked in to go back to them to look at, and I don't want to do anything that will make them turn around and blame me for!

It will not cause any problems with dealer. It will however enable you to try a known owner fix before dealer gets hands on it and gets MG involved, which (depending on dealers abilities) could get quite frustrating.

 

[tsedge]

I agree with Robf, though I wouldn't tell them you disconnected the 12V battery unless they specifically ask about that.

 

[siteguru]

If you do try this, make sure you reset the steering (1) and window (2) controls.

(1) Full left, Full right, Back to centre
(2) Fully down, Fully up, on each window in turn

 

[Kithmo]

I think it may just be that you're pressing the brake as you get in so everything is out of sequence.
I get the same if I press the brake before the main info screen (the big one) has finished booting up.
The way to avoid it is to get in, wait until the main screen has finished booting up fully, none of the icons are greyed out, then press the brake.

 

[tsedge]

My routine is also not to press the brake until the main screen is up and running.

 

[Agrajag]

I think it may just be that you're pressing the brake as you get in so everything is out of sequence

It's definitely not that. Even if it was, the user experience of "oh you pressed the brake too soon, now I'm going to display every fault possible and not let you start the car for 20-30 minutes" isn't acceptable.
The short version of what happens is:

1. Unlock the car. Do not hear the usual clicking noises (other than the door unlocking)
2. Sit down, get a dashboard full of errors, battery SoC does not display
3. Wait 20-30 minutes. Battery SoC appears and then I can start the car

 

[Kithmo]

It's definitely not that. Even if it was, the user experience of "oh you pressed the brake too soon, now I'm going to display every fault possible and not let you start the car for 20-30 minutes" isn't acceptable.
The short version of what happens is:

1. Unlock the car. Do not hear the usual clicking noises (other than the door unlocking)
2. Sit down, get a dashboard full of errors, battery SoC does not display
3. Wait 20-30 minutes. Battery SoC appears and then I can start the car

Definitely requires some diagnostics on it.
I would try disconnecting the 12v first though, that may be all the dealer does and if it works then they will take the credit and the fault may re-appear later.

 

[Agrajag]

disconnecting the 12v first though, that may be all the dealer does and if it works then they will take the credit and the fault may re-appear later.

To be clear, it is already an intermittent fault, it has been happening 1-2 times/week (though it happened twice yesterday). Other times it is fine. The first time it went to the dealer they couldn't reproduce it and just updated all the software and claimed it was fixed. Even if I disconnected 12V myself I won't know if it's fixed it until I drive it for a few weeks with no problem.

 

[gaza123]

thanks for the info - I think I likely wont do this myself as it's already booked in to go back to them to look at, and I don't want to do anything that will make them turn around and blame me for!

What did the dealer say? Mine is in the dealers now getting "fixed". Did they find out what was causing it?

 

[Agrajag]

What did the dealer say? Mine is in the dealers now getting "fixed". Did they find out what was causing it?

Mine is still at the dealers, 3 weeks now. The first day they said MG had given them a software patch which they applied, I told them to please make sure it had fixed the issue, so they kept it another day to check. The next morning they called and said they'd reproduced the issue, so the patch had not worked. They contacted MG who are sending a new control module. I guess it's on a slow boat or something

Did you have similar symptoms? In the days leading up to taking it to the dealers I went and unlocked the car every hour or so to try to reproduce and was able to reproduce it every day. It also started taking longer to "fix" itself - a couple of times 4-5 hours.

 

[gaza123]

No symptoms at all, just that the car would cut out randomly, and would display hv battery shut off, and vehicle control fault!