PHEV - Key Fob not working after battery replacement

[IKE]

I’ve just replaced the key fob battery but it’s not working. The battery (tested with my meter and is the correct voltage - i.e. not flat) is in the correct way round, there‘s been nothing damaged within the key, and the spare key works fine (so it’s not the car). If it needs re-pairing, does anyone know how to do that? The usual on-line searches suggest putting the key in the ignition, blah, blah blah, but, of course, the PHEV does not have an ignition key-slot.
Any ideas?
Thanks.

 

[Jto]

Did you read the manual on how to replace the battery then what to do after.

 

[IKE]

Yes, as per the manual (p 136): after inserting new battery and refitting the cover, “Set the vehicle power system to READY to resynchronise the key with the vehicle.”
Tried that - no joy.
Then thought perhaps change the battery whilst in the car (perhaps it needs to reset when it all clicks together inside the car), with the power system to READY. Of course, with the main key not working, you have to use the other key to get in, start up, and wait for READY. But now you have both keys in the car, but the “new one” hasn’t synch’d. There is no beep, or on-screen message to let me know that it’s done anything. So, I’m asking if anyone has actually performed the re-synching, and let me know how they did it.
Thanks

 

[Lovemyev]

I’ve just replaced the key fob battery but it’s not working. The battery (tested with my meter and is the correct voltage - i.e. not flat) is in the correct way round, there‘s been nothing damaged within the key, and the spare key works fine (so it’s not the car). If it needs re-pairing, does anyone know how to do that? The usual on-line searches suggest putting the key in the ignition, blah, blah blah, but, of course, the PHEV does not have an ignition key-slot.
Any ideas?
Thanks.

Here is a very quick video showing the process of replacing the battery.
Read below in the comments of this video, and there is a guy who has had the same problem when replacing the fob battery in his HS also.
It would appear that the quality of the replacement batteries is very important.
From experience, I can truly tell you that i have stopped buying cell coin batteries from either E.bay or Amazon anymore, because there are just WAY too many fakes in the system these days.
I only buy from a major retail store now.
The last batteries I bought from E.Bay only lasted 3 days and the car reported that they needed replacing.
I was stating to think that it was the car was at fault, after changing two batteries in less than a week !.
I replaced the last faulty one, with a battery I bought from Tesco's and it was still working correctly six months latter, when I sold the car.
My son had the similar thing with his VW Tiguan last summer, when the Duracell batteries he bought online, kept flagging up a low battery fob warning on the dash of the car.
This happened twice, one after the other !.
I replaced this so called genuine battery out, and fitted another good known new battery, the warning cleared instantly !.
I seem to remember that VW suggested that the coin cell battery should be replaced while sitting in the car.
Not sure if this is necessary on the MG system though.

Top Tip :- Can I strongly suggest that you purchase a new battery from a GOOD know source and try replacing it again !.
Don't buy them online.

 

[IKE]

Good call re dud batteries. I have a card of three Panasonic batteries. I tried the first “new” battery after trying previous other makes but this one didn’t work. I’ll try the other two tomorrow. My Panasonics look like they are the real thing but I honestly can’t remember where I bought them. It’s very likely it was eBay or Amazon.
I‘ll post an update.

 

[Lovemyev]

Good call re dud batteries. I have a card of three Panasonic batteries. I tried the first “new” battery after trying previous other makes but this one didn’t work. I’ll try the other two tomorrow. My Panasonics look like they are the real thing but I honestly can’t remember where I bought them. It’s very likely it was eBay or Amazon.
I‘ll post an update.

Only buy from a good know retailer my friend !.
They are going to be more expensive of course, but you have to be 100% certain of there origin or it could be both embarrassing and wasted trip to the dealership for a simple battery replacement.
Good luck and report back please !.

 

[Daveap]

I have just changed my key fob batteries for gen 1 MG ZS EV as the voltage was indicating 2.8v - not bad after nearly 4 years.

One key fob is fine the other fails to work that correlates with the experience of IKE. Good quality button cell replacements were used.
I have tested the key fob and the voltage is good. In addition. I note that when I press any of the buttons a red LED lights up on the internal pub but there is no RF output from the RF module (as tested with a spectrum analyser).

I shall now try to ascertain whether it requires to be paired or replaced. On this fob the only difference in approach was I left the key fob for a couple of days before inserting the new button cell - is this a factor?

Grateful for any ideas before I go down the dealer pathway.

 

[Lovemyev]

If you intend to go down the dealer route, then it is my understanding that the keys are coded in pairs !.
Don’t forget to take your spare key ?.

 

[ger]

Someone might of already suggested this but if the spare fob works put that battery into the one that is faulty and prove battery or Fob.
Good luck

 

[Spinynorman]

Aren’t fob batteries meant to be changed every service? Type 1 & type 2 service?
I’ve just had to change both my batteries recently after nearly 4 years of use, so fair do’s, I suppose.
But I never had to do any re-sync or anything. Just pointed at the car and unlocked first time after total failure. I’ve A ZS-EV Gen 1 - 20 plate
I’m marking my batteries so that the next time it’s serviced I’ll know…
Hate being taken for a ride with expensive promised servicing with no checklist supplied on completion.
Won’t happen in future, I can tell you!

 

[allancoblu]

Appreciate this is late for OP, but just in case anyone else faces a similar issue here's the solution, my partner just received a new fob and had the same problem, could open the doors but key wasn't found by the system.
Somewhere in the back of mind I remembered that it has to be synced, and to do that you place the fob in the bottom of the drinks holder in the centre console, press the start button and it resyncs.
Hope this might be of use to someone in the future.