The car appears completely dead?

Use this guide only with the vehicle stationary and secured. Battery location, access points, earth points and emergency-start procedures vary by model and year. Use the handbook for your exact vehicle; photographs or terminal locations from another MG are not substitutes.

1. Check the situation before touching anything

1. Confirm the car is safely parked and cannot roll.
2. Look from a distance for damage, fluid, exposed orange cables, heat, smoke or unusual noise.
3. Keep the remote key and connected-car app from sending repeated commands.
4. If the vehicle has been submerged or seriously damaged, stop and use trained recovery professionals.

UK recovery guidance stresses that electric vehicles can remain hazardous when damaged and that their high-voltage layout differs by model. Orange high-voltage cabling and traction-battery components are not owner-service items.

2. Separate the likely symptoms

• One key fails but the other works: investigate the key or its coin cell, not the vehicle battery.
• Neither key works and no lights or screens respond: a low 12-volt supply is one possibility, but not a confirmed diagnosis.
• Interior lights work but the vehicle will not become ready: read the exact warning; do not assume that a jump start is the answer.
• “12V Battery Charging System Fault” appears: MG’s MG4 manual lists this as a fault requiring an authorised repairer as soon as possible.
• The app alone is stale: use the iSMART connection guide; stale remote data does not prove the car is dead.

3. If normal unlocking fails

1. Try the spare key once, if available.
2. Check the exact handbook for the mechanical-key release and door-access method.
3. Do not prise handles, force windows or copy an online method for a different model.
4. If you cannot safely access the vehicle or the handbook is unavailable, call MG Assistance, your breakdown provider or an MG retailer.

A flat key battery and a discharged vehicle 12-volt battery can look similar from outside. Establishing which key works is useful evidence.

4. If your exact handbook permits 12-volt emergency starting

The MG4 owner manual says never to push- or tow-start the vehicle, requires approved booster cables and two 12-volt batteries, and warns to keep sparks and flames away. Its procedure uses positive-to-positive, then donor negative to a specified unpainted earth point on the disabled vehicle away from the battery and brake lines. Disconnection is in reverse order, with the black lead removed from the disabled vehicle first.

If the location, polarity, approved earth point or sequence is not completely clear for your car, stop. A breakdown professional is the safer route. Never touch orange cables, open the traction battery, use an unapproved voltage, or connect a charger/booster whose instructions are incompatible with the vehicle handbook.

5. After electrical power returns

1. Confirm the vehicle is secure and read every warning before moving it.
2. Do not assume the original cause is fixed merely because the screens illuminate.
3. If the handbook procedure was used, follow its instructions for cable removal and the required powered-on period.
4. Check that steering, braking, parking brake and gear selection show normal status.
5. If warnings remain, the vehicle repeatedly dies, or it will not become ready after the permitted attempts, contact an MG authorised repairer or recovery provider.

The MG4 manual says its intelligent-charging function may automatically use the high-voltage battery to maintain the 12-volt battery under some conditions, but it is suspended when faults are present, during starting or external charging, and when traction-battery state of charge is low. That feature is not proof that a weak auxiliary battery cannot occur.

6. Record evidence before it disappears

• model, trim, registration year and recent journey/charging history;
• which keys worked and whether the mechanical key was required;
• which lights, handles, screens or sounds responded;
• exact warning wording and 12-volt reading if the vehicle displayed one;
• traction-battery state of charge last known from the car, not only the app;
• temperature, date, time and how long the vehicle had been parked;
• any approved recovery equipment used and whether the fault returned.

Do not publish registration numbers, VINs, home locations or photographs showing security details. A redacted repeat-fault report can be sent through the MyMGEV contact form.

7. Reduce repeat failures

• Act on a 12-volt charging-system warning rather than clearing or ignoring it.
• Do not leave accessories powered contrary to the handbook.
• Keep every supplied access device usable and know where the handbook’s mechanical-access section is.
• Carry the correct breakdown details and vehicle emergency-response information.
• Ask an MG retailer to test the auxiliary battery and charging system after repeat symptoms.

Sources and scope

Reviewed 8 September 2026. This guide does not provide one universal jump-start sequence because MG models differ. It distinguishes low-voltage symptoms from high-voltage hazards and sends owners back to model-specific instructions.

• MG Europe: MG4 owner manual—intelligent charging, warnings and emergency starting
• Department for Transport: recovery operators working with electric vehicles
• Health and Safety Executive: electric and hybrid vehicles
• MyMGEV: how we check information