Disconnect and Reconnect the Battery

Disconnecting the 12 V battery on your Isuzu D-Max (TF, 2012–2020) is a job the tough little pickup makes easy, needing only a spanner and a steady, methodical approach. Owners do it to fit a new battery, to lay the truck up over a quiet spell, to work near the airbags or wiring, or to reset the electrics after a jump-start. There is no mystery to it: as long as you break and remake the connections in the right order, the D-Max powers down and relearns its settings cleanly, and the only things lost are a couple of presets you can key straight back in.

Where the 12 V Battery Is

The 12 V battery on the D-Max sits in the engine compartment, in the usual front corner. Open the bonnet, prop it securely, and look for the battery in its tray with a clamp holding it down. Identify the posts before you touch anything: the negative (−) is the black earth lead bolted to the body, and the positive (+) is the red post, usually under a hinged red cap. Being sure which is which is all it takes to keep the job clean and spark-free.

Before You Start

• Turn the ignition fully off, take the key well away from the truck, and close the doors so the electrics settle.
• Switch off the lights, blower, radio and accessories so there is no load on the battery.
• Note the radio security code, presets and clock in case the head unit prompts for the code on power-up.
• Give it a couple of minutes for the control modules to power down before disconnecting.
• Have the correct spanner ready, and wear gloves and eye protection at the terminals.

Disconnecting the Battery

1. Confirm the ignition is off and every consumer is switched off.
2. Loosen the clamp on the negative (−) terminal first, ease the lead off, and move it aside so it cannot spring back onto the post.
3. Now undo the positive (+) lead and keep it clear of any bare metal.
4. If you are working near the airbags or seat-belt pretensioners, wait a few minutes after disconnecting before going near them.

Reconnecting and Re-initialising

1. Fit the positive (+) terminal first and tighten the clamp fully.
2. Fit the negative (−) terminal last and tighten it — a loose earth is the usual cause of odd faults afterwards.
3. Make sure the hold-down clamp and both terminals are firm, then close the covers.

What You’ll Need to Reset Afterwards

The D-Max needs a few items relearned once power is back:

• Power windows — the one-touch function usually needs re-initialising; hold each switch at the fully closed and fully open limits for a moment. The steps are in our window guide below.
• Clock and radio — re-enter the time and preset stations, and the security code if it is requested.
• Warning lights — any that appear at first generally self-clear once the truck has driven a short distance.

Fit a like-for-like 12 V battery of the correct size and rating — the D-Max runs a hungry diesel starter, so it is worth matching the original capacity rather than dropping to a smaller unit. No special coding is needed on this model.

If a Warning Light Stays On or the Car Feels Off

• Check both clamps are tight and clean — a poor earth imitates all sorts of electrical faults.
• Take a short drive so the modules can relearn and settle.
• Redo the window relearn if one-touch has not come back.
• Rule out a genuinely flat or aged battery — reconnecting will not revive one that was already failing, and a diesel is unforgiving of a weak battery.
• If a light persists, it has stored a code — read it and look it up.

Frequently Asked Questions

Where is the battery on an Isuzu D-Max?

In the engine compartment, in the usual front corner. Lift the bonnet and you will find it in its tray, held by a clamp, with the negative (−) black lead and the positive (+) red post under its cap.

Which terminal do I disconnect first?

The negative (−) comes off first and goes back on last; the positive (+) is reconnected first. That order keeps you safe from sparks and short circuits while you work.

What needs resetting afterwards?

Mainly the one-touch power windows, plus the clock and radio presets and, if prompted, the security code. A stray warning light usually clears itself after a short drive.

Does a new battery need coding on the D-Max?

No. A like-for-like replacement of the correct size and rating simply fits and works — just match the original capacity for the diesel starter. There is no dealer coding step for a standard 12 V battery here.

Will disconnecting the battery clear stored fault codes?

It can clear some temporary codes and reset adaptations, but a real fault will log its code again once the truck sees the condition. It is not a fix on its own.

Can I jump-start it instead of disconnecting?

Yes — to recover from a flat battery, a jump-start avoids disconnecting entirely. You would only remove the battery for renewal, storage, or electrical work.

To relearn the windows, see our D-Max power-window initialisation guide. If a warning light stays on, decode it on autodtcs.com.