Disconnect and Reconnect the Battery

Last updated: June 5, 2026

Disconnecting the 12 V battery on a Toyota Yaris Mk4 (XP210, 2020–present) is a straightforward job for a battery change or before electrical work. There is no dealer registration to worry about, but a couple of driver-assist settings need a quick relearn afterwards. This guide covers the safe order of work for the petrol Yaris.

Note: this guide is for the 12 V battery of the petrol Yaris. On the Yaris Hybrid the same 12 V auxiliary battery procedure applies, but never touch the orange high-voltage system — that is dealer/technician work.

Where the Battery Is

The 12 V battery is in the engine bay (on the hybrid it is a small AGM-type battery, also in the engine bay rather than the boot). Lift any cover to reach the two clamps. Fit a like-for-like battery if you are renewing it.

Before You Disconnect

• Note your radio stations and personal settings (and any audio security code, if used).
• Turn the ignition off and make sure all electrical consumers are switched off.
• After switching off, wait 2 minutes before disconnecting — this lets the modules power down cleanly.
• If working near airbags or seat-belt pretensioners, allow the system to discharge before handling those parts.

Disconnecting — Correct Order

1. Turn the ignition off and wait 2 minutes.
2. Slacken the negative (−, earth) terminal first and lift the lead clear.
3. Only undo the positive (+) terminal if you are removing the battery completely.
4. If removing the battery, undo the hold-down clamp and lift it out upright.

Reconnecting — Correct Order

1. Refit the battery and secure the hold-down clamp.
2. Connect the positive (+) lead first, then the negative (−) earth lead last. Tighten both firmly.
3. Turn the ignition on for a few seconds before starting the engine.

Initialise the Parking-Assist System

After reconnecting, the Yaris’s parking-assist/steering reference needs a quick relearn so the parking sensors and steering-related assists work correctly:

1. Park on level ground and turn the ignition on.
2. Apply the parking brake and depress the brake pedal.
3. Move the gear lever to P.
4. Turn the steering wheel fully to the right, then fully to the left.
5. Return the wheel to centre. The system has now relearned its reference.

What Else to Reset

• Reset the date and time and reprogram your radio stations and preferences.
• Re-initialise the tyre-pressure system once your pressures are correct (see our Yaris TPMS reset guide).

If a Warning Light Stays On

One or two lights right after reconnecting is normal and should clear on a short drive (or after the steering relearn). If the airbag, ABS or engine light stays on, a fault code was logged — reading it needs an OBD scanner, and you can look up what a Toyota code means on our sister site autodtcs.com.

Frequently Asked Questions

Do I need to register a new battery on a Yaris Mk4?

No — Toyota does not require battery coding on this model. Fit the correct battery, reconnect, and restore your settings.

Why do the parking sensors or assists act up after a battery change?

The system loses its steering reference. The full-right-then-left steering sweep above relearns it; a short drive completes the calibration.

How long should I leave it disconnected to reset the electronics?

Around 10–15 minutes with the doors shut lets the modules power down fully.

Is the Yaris Hybrid the same job?

The 12 V auxiliary battery follows the same order. Never touch the orange high-voltage system — that is dealer/technician work.

To clear the service reminder after maintenance, see our Toyota Yaris service indicator reset guide.