Key fob not working after changing

P6cat

Standard Member
Joined
Jun 2, 2021
Messages
29
Reaction score
22
Points
23
Location
North Wales
Driving
Hi all
I have just tried to open my ZS mk1 2020, and the key fob doesn’t work this is the second time I’ve had this happen.
It was after a full charge on 7kW home charger on both occasions, I tried the spare key fob with no luck ,l tried the door button and the dash lite up saying charge complete but do not open.
So I switched the charger back on and started charging a bit more, after a couple of minutes it responded to the key fob on opened as normal.
My model doesn’t change on a home charger unless it’s locked but will charge on a rapid charger when open .
It just had its 4th year service a few weeks ago, i don’t know if it’s had any updates then.
Anybody else had similar experience of this ?
 
Last edited by a moderator:
I wonder if in the service they did some poking under the bonnet and somehow disturbed the DC-DC wiring. Possibly the connector with the CAN bus wires. But it would have to be intermittent for the second charge to have allowed entry. Does the 12V battery voltage rise to the LED between 13V and 14V when AC charging? When in ready mode?

Another possibility is that they may have failed to tighten the 12V battery terminals, if they had reason to disconnect one or both. That's an easy DIY fix.

Perhaps check if they replaced the key fob battery. Perhaps they used stale cells, or introduced grease. Can you open the door with the door buttons?

Finally, in a car this age, the 12V battery could be on its last legs, not holding a charge. Check the 12V battery voltage with a multimeter. When it stops being charged (no longer AC charging, or no longer in ready mode), how quickly does the voltage drop below 12.6V? It's normal for the voltage to drop from >13V to around 12.6V in ten seconds to a minute, but if it's been recently charged, it should not drop below say 12.2V in less than ten minutes or so.

Can you see a date stamp on the 12V battery?

One would hope that a poor 12V battery would be noticed in a service, but I can imagine it being overlooked.

As an interim solution, an overnight charge with an ordinary 12V battery charger might keep it going for a while, if it's not holding a charge properly. I believe that since msin battery charging can take many hours, charging the 12V battery while AC charging occurs at a lower voltage than when in ready mode. They may not be temperature compensating this voltage as well. All these factors could be compounding.
 
I wonder if in the service they did some poking under the bonnet and somehow disturbed the DC-DC wiring. Possibly the connector with the CAN bus wires. But it would have to be intermittent for the second charge to have allowed entry. Does the 12V battery voltage rise to the LED between 13V and 14V when AC charging? When in ready mode?

Another possibility is that they may have failed to tighten the 12V battery terminals, if they had reason to disconnect one or both. That's an easy DIY fix.

Perhaps check if they replaced the key fob battery. Perhaps they used stale cells, or introduced grease. Can you open the door with the door buttons?

Finally, in a car this age, the 12V battery could be on its last legs, not holding a charge. Check the 12V battery voltage with a multimeter. When it stops being charged (no longer AC charging, or no longer in ready mode), how quickly does the voltage drop below 12.6V? It's normal for the voltage to drop from >13V to around 12.6V in ten seconds to a minute, but if it's been recently charged, it should not drop below say 12.2V in less than ten minutes or so.

Can you see a date stamp on the 12V battery?

One would hope that a poor 12V battery would be noticed in a service, but I can imagine it being overlooked.

As an interim solution, an overnight charge with an ordinary 12V battery charger might keep it going for a while, if it's not holding a charge properly. I believe that since msin battery charging can take many hours, charging the 12V battery while AC charging occurs at a lower voltage than when in ready mode. They may not be temperature compensating this voltage as well. All these factors could be compounding.
Thanks for all your advice I will try your suggestions
It did not respond to the door buttons when the key fob is with me.
I did about 120 miles today and it seems fine the remote worked first time all day
I will check the 12V battery with a multi meter and the remote battery although both remotes didn’t work after charging the car.
Thanks again for your input
 
Last edited by a moderator:
Support us by becoming a Premium Member

Latest MG EVs video

MG Hybrid+ EVs OVER-REVVING & more owner feedback
Subscribe to our YouTube channel
Back
Top Bottom