Disconnect and Reconnect the 12V Battery

Disconnecting the 12-volt battery on a Nissan Navara (D40, 2005–2015) — the Nissan Frontier in North America — to replace it or before electrical work is straightforward, but doing it in the right order avoids blown fingers, lost presets and a re-arming immobiliser. Diesel D40s draw a big cranking current, so the terminals are chunky — use the right spanner.

Before You Start

• The 12V battery is under the bonnet. Diesel V6 models may have a second battery — disconnect both if fitted.
• Switch everything off, remove the key and close the doors.
• Have your radio/clock settings to hand; presets and the clock are lost when power is cut.

Disconnect

1. Turn the ignition OFF and wait about a minute so the modules power down.
2. Loosen and remove the negative (−) terminal first, and tuck the cable clear so it cannot spring back onto the post.
3. Remove the positive (+) terminal.
4. If removing the battery, undo the hold-down clamp and lift it out — it is heavy.

Reconnect

1. Fit the battery and connect the positive (+) terminal first; tighten it.
2. Connect the negative (−) terminal last; tighten it.
3. Do not start yet — turn the ignition ON for a few seconds so the modules wake in order, then start.

What to Relearn Afterwards

• Immobiliser: the NATS security light resumes its normal delay-then-blink and the truck recognises your key as usual — no action needed.
• Power windows: re-initialise the one-touch auto function on each window — fully raise the glass and hold the switch up for about two seconds, then fully lower it and hold the switch down for about two seconds.
• Clock and radio: reset the clock and re-save your stations.
• Diesel idle: the engine may idle slightly unevenly for the first few minutes while the ECM re-adapts — this settles on its own with normal driving (the petrol-engine “idle air volume relearn” procedure does not apply to the diesel).

Frequently Asked Questions

Which terminal comes off first? Negative (−) off first, and negative on last. This avoids a spanner shorting the live positive post to the bodywork.

Does my Navara have two batteries? Some diesel V6 D40s do — check under the bonnet and disconnect/reconnect both, negative-first and negative-last on each.

Do I need a radio code? Most D40 head units do not need a code, but you will lose the clock and saved stations.

The idle is a bit lumpy after reconnecting — is that a problem? Not usually — the diesel ECM re-adapts over the first few minutes of driving. If it stays rough, have it checked.

If a warning lamp stays lit after reconnecting and you want to check the code, visit our sister site autodtcs.com.