These instructions apply to the Daihatsu Sirion Mk2 (M3) 2005-2011.
For other models, please choose your vehicle here.
Disconnecting the 12 V battery on your Daihatsu Sirion (M3, 2005–2011) is a quick, owner-friendly job that needs little more than a spanner and a few minutes. You might do it to fit a new battery, to isolate the electrics before working near the airbags or seat-belt pretensioners, to prepare the car for long winter storage, or after a jump-start. The Sirion is a light, uncomplicated supermini, and its wiring is just as simple — take the terminals off and put them back in the correct order and the car powers up cleanly, with only the clock, radio and one-touch windows to sort out afterwards.
Where the 12 V Battery Is
On the Sirion the 12 V battery lives in the engine compartment, in the usual front corner. Raise the bonnet and you will see it upright with two cables clamped to the posts on top. The negative (−) lead bolts to the black terminal and earths to the body; the positive (+) lead is on the red terminal, normally tucked under a hinged coloured cap. Fold that cap back so the post is exposed, and confirm which terminal is which before you loosen a nut — the order you work in is what keeps the job safe.
Before You Begin
- Make sure the ignition is fully off and take the key away from the car so nothing keeps a circuit awake.
- Turn off the lights, blower, radio and any accessories so there is no electrical load when you break the connection.
- Note your radio security code and preset stations if your set uses a code, so you can key it back in later.
- Give the modules a couple of minutes to power down after switch-off, and wait longer still before going near the airbags or pretensioners.
- Have the right spanner to hand (the clamp nuts are typically 10 mm) and wear gloves and eye protection.
Find the Battery First
Disconnecting
- With the ignition and everything else off, loosen the clamp nut on the negative (−) terminal first.
- Lift the negative clamp off the post and move the cable clear so it cannot flop back onto the terminal.
- Now loosen and remove the positive (+) clamp. With the earth already disconnected the system is dead and safe to work on.
- If you are working near the airbags or pretensioners, wait a few minutes after disconnecting before you touch them.
Reconnecting
- Refit the positive (+) terminal first, seating the clamp fully on the post and nipping the nut up snug.
- Reconnect the negative (−) clamp last and tighten it.
- Check both clamps are firm and cannot be twisted by hand — a loose earth is the usual reason a car feels odd after this job.
What You’ll Need to Reset Afterwards
The Sirion loses very little memory, so the list is short:
- Clock and radio presets — reset the time and re-enter your stations, plus the security code if your set asks for it.
- Driver’s window one-touch — if the auto-up/down function drops out, hold the switch fully at each limit for a moment to relearn it.
- Warning lights — any that appear generally clear themselves after a short drive once the systems have run normally again.
If a Warning Light Stays On or the Car Feels Off
- Re-check both clamps are tight; a slightly loose connection can imitate several faults.
- Take a short, steady drive to let the systems relearn before assuming there is a problem.
- Repeat the window one-touch relearn if it still will not auto-up or auto-down.
- If the car cranked slowly or the battery is a few years old, test the battery itself before chasing wiring.
- A light that stays on has logged a code you can read to see exactly what it points to.
Frequently Asked Questions
Where is the 12 V battery on a Daihatsu Sirion?
In the engine compartment, in the usual front corner. Lift the bonnet and it stands upright with the two cable clamps on top; the positive post sits under a coloured cap.
Which terminal do I disconnect first?
The negative (−) terminal comes off first and goes back on last. Removing the earth first leaves the system dead when you handle the positive, so a slipped spanner cannot short to the body.
Will I lose my radio code?
You might, if your set is code-protected. Note the code before you start so you can re-enter it, then reset the clock and presets once the battery is reconnected.
Does a new battery need coding on a Sirion?
No. The Sirion uses a straightforward 12 V battery, so a like-for-like replacement of the correct size and rating simply fits — there is no battery registration or coding to carry out.
Will disconnecting the battery reset the service light or clear fault codes?
It may wipe some stored codes and the ECU’s learned values, but it is not a proper way to reset a service reminder and it will not cure an underlying fault — a live problem simply logs its code again once the car runs.
Can I jump-start it instead of disconnecting?
Yes, if you only need to start a flat car — jumping it leaves the terminals undisturbed. Reserve disconnecting for battery renewal, storage, or isolating the electrics for other work.
If a warning light stays on after reconnecting, look up the code on autodtcs.com.
Independent guide — not affiliated with Daihatsu. Always follow your official service manual and safety precautions. Read our full disclaimer.