These instructions apply to the Lexus IS Mk2 (XE20) 2005-2012.
For other models, please choose your vehicle here.
Disconnecting the 12 V battery on your Lexus IS (2005–2012) — the XE20 IS 250 / IS 220d / IS 200d — for a new battery, winter storage, or work near the airbags is a straightforward job. The battery is in the engine bay.
There are a handful of everyday reasons an IS owner ends up pulling the 12 V battery: fitting a fresh one when the old cells no longer hold charge, laying the car up over winter so a parasitic drain can’t leave you with a flat battery in spring, doing bodywork or electrical repairs where a live system is a hazard, or safely working in the vicinity of the airbags and seat-belt pretensioners. None of it is difficult. This XE20 generation IS 250, IS 220d and IS 200d is a conventional petrol or diesel car — there is no hybrid drive on this model, so there is no orange high-voltage cabling to be wary of and no separate traction battery. Provided you take the terminals off and put them back in the correct order, the car wakes up cleanly and relearns the few things it forgets.
Where the 12 V Battery Is
The 12 V battery sits in the engine compartment, under a plastic cover. Lift the bonnet, unclip or unscrew the cover and you’ll see the two terminals: the negative (−) post carries a black lead and usually an earth strap to the body, and the positive (+) post is capped with a red cover. Take a moment to confirm which is which before you touch a spanner — the covers and the moulded “+” and “−” marks by each post make it obvious once you look.
Before You Begin
- Turn the ignition fully off and take the key well away from the car so it can’t wake the electronics.
- Switch off the lights, climate control, radio and anything else that draws current.
- Note your radio station presets and, if your audio unit asks for a security code, make sure you have it to hand.
- Give the car a couple of minutes with everything off so the modules power down before you disturb the terminals.
- Have the correct spanner ready (the clamp nuts are a common metric size) and wear gloves and eye protection.
Disconnecting Safely
- Switch everything off and confirm the ignition is out and the key is away.
- Slacken and remove the negative (−) terminal first, then tuck the lead aside so it can’t spring back onto the post.
- Now slacken and remove the positive (+) terminal.
- Working near airbags or seat-belt pretensioners? Wait a couple of minutes after disconnecting before you begin that work, so the stored energy in the system has bled away.
Reconnecting and Re-initialising
Reconnect in the reverse order: positive (+) first, then the negative (−) last, and tighten both clamps so they’re snug and won’t work loose. A like-for-like 12 V battery of the correct size and capacity needs no coding on this generation. Once power is back, the IS relearns a few items:
- Power windows — the one-touch and anti-pinch function needs re-initialising (see our IS window-reset guide).
- Steering-angle and stability settle themselves after a short drive with a few full turns each way.
- Clock and audio presets need re-entering, along with any code your radio requests.
If Something Isn’t Right Afterwards
- Check both clamps are properly tight — a loose terminal causes the most “odd” electrical behaviour after a battery job.
- Warning lights such as VSC usually clear on their own after a short drive once the relearns complete.
- If the one-touch windows still misbehave, re-do the window initialisation.
- The gear lever won’t leave ‘P’ after a flat battery? Use the console shift-lock release — prise off the small cover, press the button and move the lever.
- If a light stays on, it has stored a code — look it up on autodtcs.com.
Frequently Asked Questions
Where is the battery on a Lexus IS (2005–2012)?
In the engine compartment, under a plastic cover. This XE20 generation is petrol or diesel, not a hybrid, so there is no high-voltage system to avoid — just the ordinary 12 V battery with its negative and positive posts.
Which terminal do I disconnect first?
Always take the negative (−) off first and reconnect it last. On reassembly the positive (+) goes on first, then the negative. Working negative-first keeps your spanner from shorting a live positive post to the bodywork.
What needs resetting afterwards?
The power windows need their one-touch re-initialising, the steering-angle and stability systems relearn as you drive, and you’ll re-enter the clock and audio presets. Nothing else on this model needs attention after a like-for-like battery.
Does a new battery need coding on the IS?
No. A like-for-like 12 V battery of the correct capacity is a straight swap on this generation — there is no battery-registration step, so once it’s fitted and the clamps are tight you’re done.
Will disconnecting the battery clear fault codes or reset the service light?
Pulling the battery can drop some transient warnings, but it is not a reliable way to clear stored codes or to reset the service reminder — those are best cleared properly. If a light returns, read the code rather than relying on a disconnect.
Can I just jump-start it instead?
Yes, if the battery is only flat rather than being replaced. Jump-starting avoids losing your presets and the relearns. If the battery is genuinely worn out, though, fit a new one rather than repeatedly jumping it.
If the windows lost one-touch, see our IS power-window reset guide.
Independent guide — not affiliated with Lexus. Always follow your official service manual and safety precautions. Read our full disclaimer.