These instructions apply to the Lexus RX Mk1 (XU10) 1998-2003.
For other models, please choose your vehicle here.
Disconnecting the 12 V battery on your Lexus RX 300 (1998–2003) — the original XU10 RX — for a new battery, winter storage, or work near the airbags is a straightforward job. The battery is in the engine bay, and provided you take the terminals off and put them back in the right order, this first-generation RX relearns the few settings it loses within a short drive.
Owners usually pull the XU10’s battery for a straight renewal when it’s cranking slowly, to stop a slow drain flattening the car over winter storage, before doing electrical or bodywork jobs, or to power the car down cleanly after a jump-start. The original RX 300 is a petrol V6, not a hybrid, so there is only the one 12 V battery and no high-voltage system to be careful of — the later hybrid RX arrived on the next generation.
Find the Battery First
Identify the terminals before you loosen anything: the negative post carries a black cover and a − symbol, the positive is red and marked +. Removing the plastic cover gives you clear access.
The 12 V battery is in the engine compartment, under a cover (this RX is petrol, not a hybrid). Note your radio presets before you start.
Before You Start
- Switch the ignition fully off and take the key away from the car.
- Turn off the headlights, climate, radio and any accessories so nothing is drawing current when you break the connection.
- Write down your radio presets and note any security-code details in case you’re asked for them on power-up.
- Give the modules a minute or two to power down after switching off.
- Have the right spanner (usually 10 mm), gloves and eye protection ready.
Disconnecting Safely
- Switch everything off and confirm the ignition is dead.
- Disconnect the negative (−) terminal first, lift the clamp off the post and tuck the cable clear so it can’t spring back onto the terminal.
- Then disconnect the positive (+) terminal.
- Working near airbags or seat-belt pretensioners? Wait a couple of minutes after disconnecting before starting such work, so the airbag system fully discharges.
Reconnecting and Re-initialising
Reconnect in reverse: positive (+) first, then negative (−) last, and tighten both clamps firmly — a loose terminal is the most common reason a car feels wrong afterwards. The RX then relearns a few items as you drive:
- Clock and radio presets — reset the time and re-store your stations.
- Steering angle / stability — settles after a short, steady drive with a full lock each way.
- Power windows — if one-touch is lost, pull the switch up and hold at the fully-closed position for a moment to re-teach it.
If Something Isn’t Right Afterwards
- Check the clamps are tight first — most post-disconnect gremlins are simply a loose terminal.
- Warning lights usually clear after a short drive once the systems re-check themselves.
- Redo the window relearn if auto-up hasn’t come back.
- The gear lever won’t leave ‘P’ after a flat battery? Use the console shift-lock release — see our RX shift-lock release guide.
- A persistent light stores a code — look it up on autodtcs.com before spending money.
Frequently Asked Questions
Where is the battery on a Lexus RX 300 (1998–2003)?
In the engine compartment, under a cover. The original XU10 RX is petrol only, so there’s just the one 12 V battery and no high-voltage system to avoid.
Which terminal do I take off first?
Negative (−) off first when disconnecting, and reconnect it last. Positive (+) goes back on first. That order stops a spanner shorting to the body while the battery is still live.
What needs resetting afterwards?
The clock and radio presets, the one-touch windows, and the steering-angle learn. Most of it settles on a short drive; the windows may want a quick pull-and-hold to restore auto-up.
Do I need to wait near the airbags?
Yes — give it a couple of minutes after disconnecting before working on the airbags or seat-belt pretensioners, so the system fully discharges first.
Does a new battery need coding on this RX?
No. A like-for-like 12 V battery on the XU10 is a straight swap with no registration step. Fit it, reconnect in the right order and let the car relearn its settings.
Will disconnecting the battery clear my fault codes or service light?
It can drop temporary codes and reset some trip data, but a fault that’s still present will just log again and relight the warning. Disconnecting is not a proper service reset or a cure for a real fault — find the cause instead.
Independent guide — not affiliated with Lexus. Always follow your official service manual and safety precautions. Read our full disclaimer.