These instructions apply to the MG ZS Mk1 (ZS11) 2017-2021.
For other models, please choose your vehicle here.
The MG ZS (2017–2021) came with two ignition systems depending on trim. Higher trims (such as Exclusive, and the ZS EV) have keyless start — a START/STOP button you press with the fob in your pocket. Lower petrol trims (such as Explore/Excite) use a conventional bladed turn-key in an ignition barrel. Which one you have decides exactly how to cope with a dead key-fob battery.
Keyless ZS: Start It With a Dead Fob
On a keyless ZS the fob normally talks to the car by radio. When the coin cell dies the dash shows a key-warning message and pressing START does nothing — but the car can still read the fob’s passive transponder at very close range.
- Get in first with the emergency key blade (see below) and sit in the driver’s seat.
- Press the brake pedal fully and hold it.
- Hold the fob flat against the START/STOP button so the chip sits right on it. The button may beep or its ring may change as the car detects the fob.
- While still holding the fob there, press the START button. The engine starts.
If it does not catch first time, turn the fob over and present the other face squarely to the button — the antenna behind it only reaches a centimetre or two.
Turn-Key ZS: a Dead Battery Barely Matters
If your ZS has a key you twist in a barrel, the fob battery only powers the remote lock/unlock buttons. The cut key carries a transponder the immobiliser reads with no battery, so you simply insert the key and turn it to start as you always do. A flat coin cell only costs you the remote buttons until you replace it.
Unlock the Door With the Emergency Key
A dead fob will not work the central locking by radio, so use the hidden metal blade.
- Press the small release catch on the fob and slide out the emergency key blade.
- Insert the blade into the driver’s door lock cylinder (behind a cap on the handle on some builds) and turn to unlock.
- Opening the door this way may trigger the alarm; starting the car with a recognised fob stops it.
Why the Chip Still Starts the Car
The fob holds two systems: a battery-powered radio for the remote buttons, and a battery-free transponder chip read by the immobiliser. Holding the fob on the START button (or turning the cut key) lets the car’s antenna energise that chip and read its code, so a totally flat coin cell still allows starting — it only kills the remote-lock radio.
Replace the Coin Cell
Restore normal operation with a fresh battery.
- Slide out the emergency key blade, which releases the fob cover.
- Twist or prise the two halves apart at the seam.
- The ZS fob typically uses a CR2032 3V lithium coin cell (some MG fobs use a CR2025 — check the old one).
- Fit the new cell the same way up, clip the case shut and refit the blade. Stand by the car and press a button to re-sync.
Frequently Asked Questions
How do I tell whether my ZS is keyless or turn-key? If you press a START/STOP button, it is keyless. If you twist a key in a barrel, it is the bladed turn-key system.
Which battery does the ZS fob take? Usually a CR2032 3V lithium coin cell; a few MG fobs use a CR2025. Match it to the cell you remove.
Can the emergency blade start a keyless ZS? No — the blade only unlocks the door. You must hold the fob against the START button to start a keyless car.
The remote buttons died but the turn-key car still starts — is that normal? Yes. On a turn-key ZS that is exactly what a flat fob battery looks like. Fit a new cell to restore the buttons.
Does the ZS EV use the same method? Yes — the electric ZS is keyless and uses the same hold-the-fob-to-the-button backup, then press START with your foot on the brake.
If a warning light stayed on after you got going, you can look up the exact fault code on our sister site autodtcs.com to see whether it relates to the keyless system or something unrelated.
Independent guide — not affiliated with MG. Always follow your official service manual and safety precautions. Read our full disclaimer.