These instructions apply to the Isuzu MU-X Mk1 2013-2020.
For other models, please choose your vehicle here.
If the remote for your first-generation Isuzu MU-X (2013–2020) has started working only from a metre away, feels hit-and-miss, or has stopped responding altogether, the cause is almost always the little coin cell inside the fob rather than anything on the car. The MU-X of this era shipped with two different remotes depending on trim: a folding “flip” blade key on lower grades, and a smart (proximity/keyless-entry) fob on higher grades — the same one shared with the D-Max ute of the period. Both take the same battery, but they open differently, so it is worth knowing which one you are holding. Here is how to spot a dying cell, the exact battery to buy, and the step-by-step for each fob type.
How to Tell the Fob Battery Is Dying
- Shrinking range. You have to be right beside the MU-X — or almost touching the door handle with the fob — before it will lock or unlock. This is the classic first sign.
- The LED stops flashing. The little indicator on the remote will not light on a button press once the cell is too weak — a quick way to confirm it is the fob and not the truck.
- Keyless start gets fussy. On smart-key MU-X models the car may fail to detect the fob for push-button start, or you may need to hold the fob against the start button for it to read.
- Cold-morning dropouts. A near-flat lithium cell loses voltage in the cold, so intermittent response first thing on a winter morning often means the battery is on its way out.
A CR2032 in an MU-X remote typically lasts two to four years. If yours is that old and showing any of the above, fit a fresh cell before you start suspecting the receiver or the immobiliser.
The Battery You Need
Both the flip key and the smart fob use a single CR2032 — a 3-volt lithium coin cell, and the most common fob battery there is. You will find it in any supermarket, hardware shop or petrol station. Buy a good-quality branded cell: cheap ones sag under the brief burst of current the transmitter draws and can give poor range even when box-fresh. You only need the new battery and a small flat tool to open the case.
Method 1 — Smart (Proximity) Fob
This is the keyless fob with push-button start — the same design used on the D-Max of the period.
- Release the emergency blade. Slide or press the small catch on the fob and pull the mechanical key blade straight out.
- Split the case. Insert the tip of the emergency blade (or a small flat-blade screwdriver) into the slot the blade left behind and gently twist to pop the two halves apart. Work around the seam with your fingers if it needs a little more persuasion.
- Lift out the old cell. Note how it sits, then ease it out from under its clip.
- Fit the new CR2032 positive (+) side up. The flat, marked face of the cell faces upward, away from the circuit board, on this fob.
- Close it up. Press the halves back together until they click, then slide the emergency blade home until it latches.
Method 2 — Folding “Flip” Key
This is the remote where the metal blade folds out of the fob body at the press of a button.
- Fold the blade away so the fob is easier to hold, and look for a seam or a small retaining screw on the back.
- Open the case. If there is a tiny cross-head screw, undo it with a fine Phillips driver and lift the cover. If there is no screw, prise the seam apart gently with a flat plastic tool or a coin.
- Note the orientation, then remove the cell. Look carefully at which way the flat marked face points before you take it out.
- Fit the new CR2032 the same way round as the one you removed, seat it firmly under its clip, and refit the cover (drive the screw back in snugly if there was one — don’t overtighten the plastic).
⚠️ Get the polarity right. A coin cell fitted upside down will not power the fob and can slowly discharge against the contacts. The verified orientation for the smart fob is positive up; on the flip key, always copy the orientation of the cell you removed rather than guessing.
Did It Work?
Stand back a few metres and lock, then unlock, the MU-X. Full range should return straight away and the LED should flash brightly on each press. On a smart-key model, confirm the car reads the fob for keyless entry and push-button start — if it now starts normally, the new cell has done its job.
If a Fresh Cell Doesn’t Fix It
- Re-check polarity and seating. An upside-down or loosely seated cell is the single most common reason a “new battery” changes nothing. Make sure it clicks firmly under its clip.
- Clean the contacts. A smear of finger grease or light corrosion on the terminals is enough to cause dropouts — wipe them with a dry cloth.
- Try the known-good spare. If your second key works fine on the car, the first fob’s transmitter may have failed — rare, but it happens.
- Rule out the car’s 12 V battery. A weak main battery can make the MU-X slow to wake and mimic a key fault; if the whole truck feels sluggish to respond, have the vehicle battery tested.
New Key or Spare — Why It’s a Dealer Job
Swapping the coin cell keeps the fob’s existing coding, so no reprogramming is needed and the remote works the instant the battery is in. Cutting and coding a new or replacement key is a different matter: the MU-X’s immobiliser has to be accessed with diagnostic equipment, and blank smart fobs and flip keys must be matched to the vehicle’s VIN and programmed. That makes adding a spare or replacing a lost key a job for an Isuzu dealer or an auto-locksmith — so keep the battery in your spare fresh too, and you’re never down to a single working key.
Frequently Asked Questions
What battery does an Isuzu MU-X key fob take?
A single CR2032 3-volt lithium coin cell. Both the folding flip key and the smart proximity fob used on the 2013–2020 MU-X take the same size.
Which way up does the battery go?
On the smart proximity fob the CR2032 goes in positive (+) side up. On the flip key, match the orientation of the cell you removed — take a photo before lifting the old one out if you are unsure.
Do I need to reprogram the key after changing the battery?
No. A battery swap doesn’t touch the fob’s coding, so it pairs with the car straight away. Only a brand-new or replacement key needs programming.
How long should an MU-X key battery last?
Usually two to four years. Heavy remote use, or leaving a smart fob sitting close to the car so it keeps waking, shortens that.
My fob still won’t work after a new battery — what now?
Re-check the polarity and that the cell is seated firmly, then clean the contacts. If the LED still won’t light with a known-good cell, the transmitter may have failed — but that is far rarer than a flat or upside-down battery.
Can I still drive the MU-X if the fob is completely dead?
Yes. Use the emergency blade inside the fob to unlock the driver’s door. On smart-key models, hold the fob against the start button (or the marked spot on the column) and the car can still detect the transponder to start, even with a flat coin cell.
If your remote stopped working suddenly right after the car battery was disconnected — rather than fading gradually — the cause is more likely the pairing than the cell, and a stored fault can point you the right way. You can look up any code the MU-X has logged on autodtcs.com.
Independent guide — not affiliated with Isuzu. Always follow your official service manual and safety precautions. Read our full disclaimer.