These instructions apply to the MG ZS Mk1 (ZS11) 2017-2021.
For other models, please choose your vehicle here.
The remote for an MG ZS (2017–2021, petrol/ICE) — the Zhengzhou-built crossover, not the later ZS EV, which is a separate car — that only locks the doors from arm’s length, responds erratically, or has stopped working altogether is almost always suffering from one simple thing: a flat coin cell. The ZS is sold with a three-button smart (keyless) proximity fob that hides a slim mechanical emergency blade inside it, and that same blade doubles as the tool you use to crack the case open. Here is the exact battery it takes, how to tell a dying cell from a genuine fault, the step-by-step swap, and why cutting a brand-new key is the one job you can’t finish at home.
How to Tell the Fob Battery Is Dying
- Shrinking range. You have to stand right next to the ZS — or hold the fob against the door handle — before it will lock or unlock. This is the classic first warning.
- Keyless entry gets fussy. The car stops recognising the fob in your pocket, so the request-to-enter button on the handle and the dashboard start button need several tries.
- A key-battery warning. When the smart fob’s cell is weak the ZS can show a low-key-battery message in the instrument cluster; treat it as a prompt to fit a fresh cell rather than something to ignore.
- Cold-morning dropouts. A near-flat lithium cell loses voltage in the cold, so intermittent response on a frosty morning that clears once things warm up points straight at the battery.
A coin cell in an MG ZS fob typically lasts two to four years. If yours is around that age and showing any of the symptoms above, change the cell before you start suspecting the receiver or the immobiliser.
The Battery You Need
The MG ZS smart fob takes a single CR2032 — a 3-volt lithium coin cell, the most common fob battery there is and stocked by every supermarket, hardware shop and petrol station. A handful of MG remotes have shipped with the slightly thinner CR2025 instead, so the golden rule is to read the code printed on the cell you take out and match it exactly. Both are 20 mm across; the only difference is thickness (3.2 mm versus 2.5 mm), and a CR2032 is the correct fit for the ZS fob. Buy a good branded cell — cheap ones sag under the brief high current the transmitter draws and can give poor range even when factory-fresh.
How to Change the MG ZS Smart-Fob Battery
- Release the emergency blade. Press the small catch on the side (or back) of the fob and slide the metal mechanical key straight out. It comes away completely and becomes your opening tool.
- Split the case. With the blade removed there is a slot and a visible seam running around the fob. Slip the tip of the blade — or a thin flat plastic tool — into that seam and gently twist to pop the two halves apart. It parts with a light click; you don’t need force, and forcing it risks snapping the plastic clips.
- Note the orientation, then lift the cell out. Look at which face of the coin cell is showing before you disturb it. On the ZS fob the CR2032 sits positive (+) side up, but always trust the cell you removed over any general rule.
- Fit the new cell. Drop the fresh CR2032 in the same way round, making sure it seats fully under its retaining clip against clean contacts. Handle it by the edges so you don’t leave grease on the faces.
- Close it up. Line the two halves back together and press until they click all the way round, then slide the emergency blade home until it latches. Stand by the car and press a button to confirm it responds.
⚠️ Get the polarity right. A coin cell fitted upside down won’t power the transmitter and, left in the wrong way, can quietly discharge — so copy the orientation of the cell you took out rather than guessing. If in any doubt, photograph the open fob on your phone before removing the old battery.
Confirm It Worked
Step back a few metres and lock, then unlock, the ZS. Full range should return instantly, and keyless entry and the start button should recognise the fob normally again. If a key-battery warning was showing in the cluster, it usually clears the next time the car reads a healthy fob — sometimes immediately, sometimes after one short drive cycle.
If a Fresh Cell Doesn’t Fix It
- Re-check polarity and seating. An upside-down or loosely seated cell is by far the most common reason a “new battery” changes nothing — the coin must sit firmly under its clip.
- Wipe the contacts. A smear of finger grease or light corrosion on the terminals is enough to cause dropouts; clean them with a dry cloth before blaming the fob.
- Confirm the cell is genuinely good. Batteries can sit flat on a shop shelf for years. If a second known-fresh CR2032 restores range, the first one was the problem.
- Rule out the car. If the ZS itself is slow to wake or the fob died right after the 12 V battery was disturbed, the issue may not be the cell at all — see our guide on how to start the MG ZS with a dead fob to get moving while you sort it.
New Key or Spare — Why It’s a Dealer Job
Swapping the coin cell leaves the fob’s existing coding untouched, so no reprogramming is needed and the remote works the moment the case clicks shut. Cutting or coding a new key is a different matter: a blank ZS smart fob has to be ordered against the car’s VIN, the mechanical blade cut to the lock, and the fob paired to the immobiliser with diagnostic equipment. That makes adding a spare or replacing a lost key a job for an MG dealer or an auto-locksmith — so keep the battery in your second key fresh too, and you’re never down to a single working remote.
Frequently Asked Questions
What battery does an MG ZS key fob take?
A single CR2032 3-volt lithium coin cell. A few MG remotes use the thinner CR2025, so check the code stamped on the cell you remove and match it — but a CR2032 is the correct fit for the 2017–2021 ZS smart fob.
How do I open the MG ZS fob without breaking it?
Slide out the emergency blade first, then use the blade or a thin flat tool in the seam it leaves behind to twist the two halves apart. Work gently — the case is held by plastic clips, not screws, and forcing it is what cracks them.
Which way up does the battery go?
Positive (+) side up in the ZS fob. The safest approach is simply to fit the new cell the same way the old one was sitting; take a quick phone photo before you lift it out if you’re unsure.
Do I need to reprogram the key after changing the battery?
No. A battery swap doesn’t affect the coding, so the fob and keyless entry work straight away. Only a brand-new or replacement key needs pairing to the car.
How long should an MG ZS key battery last?
Usually two to four years. A smart fob left sitting close to the car wakes constantly to answer the keyless system, which drains it faster than a remote you only press a few times a day.
Can I still drive the ZS if the fob battery is completely dead?
Yes. Use the mechanical blade hidden in the fob to unlock the driver’s door, and the keyless system is designed to still start the car with a flat fob — typically by holding the fob against or very close to the start button — so a dead cell won’t leave you stranded.
If the remote stopped responding suddenly the moment the car’s 12 V battery was disconnected — rather than fading over weeks — the cause is more likely the electrics or a stored fault than the coin cell. You can look up what any dashboard warning or stored code means on autodtcs.com.
Independent guide — not affiliated with MG. Always follow your official service manual and safety precautions. Read our full disclaimer.