Vehicle Control System Fault error

[legend99]

Hi,
If anyone could offer advice I'd be very grateful....
Driving Long Range ZS and in the middle of the road today all the string of warnings flashed up - with the main one being the Vehicle Control System Fault. String of errors about front collision system being down, hill assist being down, etc etc etc.
Nearly crashed as the car suddenly became almost impossible to drive. Brakes barely worked. Speed limited to circa 24kmph. I tried the disconnection of the 12V battery for 5 minutes - made no difference. Given that it happened mid drive, as opposed to many others a year or two ago reporting this after a charge, does anyone have any advice on what might be up? The car is only a year old.....

Thanks in advance

 

[Coulomb]

The sudden onset of many fault lights is often due to a bad 12V battery. Some cars have waited a long time for parts, and they possibly didn't have enough battery savers, or didn't realise that the wait would be so long. That might have weakened the 12V battery, and perhaps one cell shorted or collapsed to trigger this problem.

Perhaps get it checked, if it's under 12 months from sale, it should be replaced under warranty. It's annoying that the 12V battery only gets 12 months warranty.

 

[legend99]

Thanks. That had occurred to me alright. The MG app is saying the battery is 13.0v - would that imply it is less likely to be the issue?

 

[Coulomb]

The MG app is saying the battery is 13.0v - would that imply it is less likely to be the issue?

Not really. 13.0 means its voltage is likely being pushed up by the DC-DC. The acid could be like distilled water and the voltage can be 13.0V just from the DC-DC (like an ICE car's alternator). Though if you have a shorted cell, that means that the remaining 5 cells are at an average of 2.6V per cell (equivalent to 15.6V if all 6 cells were working). At that voltage, I'd expect the battery to get hot, you might hear bubbling, and gas might be venting. Absent those symptoms, it could still be a collapsed or weak cell, not able to absorb much charge or allow much discharge.

One suggestion: turn on the headlights, making sure that the car is not in ready mode or being charged. That means the DC-DC should be off, and the battery should be powering the headlights on its own. Possibly the car will fight you and turn off the headlights, I don't know. After a few minutes of the headlights running (try to judge if they are fading), use the app to measure the voltage. A healthy 12V battery should hold about 12.4V in these conditions, certainly over 12.0V, though I'm not certain. If the battery is as bad as I suspect, it will probably be lower than that, and it might even fail to keep the headlights at normal brightness for more than a few tens of seconds.

 

[Tim Green]

Good call.
probably worth trying a new 12v battery. It might save a lot of hassle....

 

[legend99]

Thanks for the suggestions. No joy - the battery didn't drop below 12.6v with the lights on and the AA now are arranging to have it lifted. Not a good start to life with an EV.

 

[legend99]

Unfortunately, I have heard nothing from the dealer where the car is now parked up other than being told it will be weeks before it is even looked at. And the MG Warranty cover does not cover a replacement car. All in all, not a good situation.

 

[legend99]

Just to give an update. Been told it a brake pump issue? From looking here, that seems to be an issue that pops up once in a while. I'm not impressed to be blunt. Essentially the brakes failed in a moving car - that's not good.

 

[kiwilion]

I also have this experience last night for the 3rd time. It's annoying to happen this to a new car. Specially after first service as well. Twice occured after charging with 25kw charger.

 

[TassieDi]

I also have this experience last night for the 3rd time. It's annoying to happen this to a new car. Specially after first service as well. Twice occured after charging with 25kw charger.

You might like to look out for a 12V battery drain problem - I have this problem when charging at home with my AC fast charger. I fitted a 12V battery monitor and through this got confirmation of the drainage issue. I'm not sure of the cause with mine, but my workaround is to unplug the car as soon as possible once charging is complete. See other posts about this.