These instructions apply to the Smart Forfour Mk2 (W453) 2014-2021. For other models, please choose your vehicle here.
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Disconnecting the 12 V battery on your Smart Forfour (W453, 2014–2021) — for a new battery, winter storage, or work near the airbags — is a straightforward job once you know where it lives. Like the Fortwo, the Forfour is rear-engined, so the 12 V battery is at the front of the car.
Find the Battery First
The engine sits in the rear, so the 12 V battery is at the front, under the bonnet/front service flap behind the front trim. Note your radio code and presets before you start.
Electric drive (EQ) models: these have a separate high-voltage system — never touch the orange high-voltage cabling. The 12 V battery is still the one you disconnect for normal work.
Disconnecting Safely
- Switch everything off, key to OFF, and remove it.
- Close all the doors and wait until the daytime running lights go out.
- Disconnect the negative (−) terminal first, then the positive.
- Working near airbags or pretensioners? Wait a few minutes after disconnecting.
Reconnecting and Re-initialising
Reconnect positive first, then negative. The Forfour then relearns a few items:
- Power windows — re-initialise one-touch (hold the switch at the limits).
- Re-enter the clock and radio presets.
- The service and TPMS displays settle after a short drive.
If Something Isn’t Right Afterwards
- Warning lights often clear after a short drive.
- A persistent light stores a code — look it up on autodtcs.com.
- Fit a like-for-like battery of the correct size and rating.
Frequently Asked Questions
Where is the battery on a Smart Forfour W453?
At the front of the car, under the bonnet/front service flap — the engine is in the rear.
Which terminal first?
Negative (−) off first, reconnect it last.
Is the electric Forfour different?
The EQ has a separate high-voltage system — don’t touch the orange cabling; you still service the 12 V battery.
Do I need to recode anything?
Windows may need a one-touch relearn, and you’ll re-enter the clock and presets.
If a warning light stays on after reconnecting, look up the code on autodtcs.com.
Disclaimer: The information on this page is provided for general guidance only. Always follow your official service manual and safety precautions when working on your vehicle. We are not responsible for errors, omissions, or any damage resulting from the use of this information.
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