Replace the Key Fob Battery

When the remote on a Volkswagen Tiguan Mk2 (AD1, 2016–present) starts working only from arm’s length, needs a second press to lock the car, or throws a “Key battery low” message in the driver display, the cause is nearly always the little coin cell inside the fob. This second-generation Tiguan sits on the VW Group MQB platform and ships with the familiar VW folding “switchblade” remote — the one whose metal blade flicks out at the press of a button — with KESSY keyless entry and go offered on higher trims. Both use the same battery and open the same way. Here is exactly how to change it, how to be sure the fob (not the car) is the problem, and why cutting a brand-new key is the one part of this job you can’t finish yourself.

How to Tell the Fob Battery Is Dying

• Shrinking range. You have to stand right next to the Tiguan — or hold the fob against the door handle — before it responds. This is the first and most reliable warning sign.
• A “Key battery low” message. The Mk2’s instrument cluster / driver display shows a low key-battery warning when it reads a weak fob, most often on KESSY keyless cars where the car is constantly polling the key.
• Buttons need repeating. One press does nothing, a second works — a classic sign of a cell that can no longer deliver the brief burst of current the transmitter needs.
• Worse in the cold. Lithium cells lose punch at low temperature, so a fob that’s fine in summer can drop out on a frosty morning when it’s already near flat.
• Keyless start hesitates. On KESSY cars you may have to hold the fob against the steering column or start button for the car to recognise it — the keyless field has the shortest range of everything the fob does, so it fades first.

A CR2032 in a Tiguan remote typically lasts two to three years. Keyless (KESSY) fobs tend to sit at the shorter end because the key wakes every time it senses the car nearby. If yours is a couple of years old and doing any of the above, fit a fresh cell before you suspect the receiver or immobiliser.

The Battery You Need

The Tiguan Mk2 fob takes a single CR2032 3-volt lithium coin cell — the standard flat 20 mm cell sold in any supermarket, hardware shop or petrol station. The switchblade remote and the KESSY keyless fob use the same cell, so you don’t need to know which one you have before buying. Fit a good-quality branded cell: cheap cells sag under the short high-current pulse the transmitter draws and can give poor range even straight out of the packet. Don’t substitute a CR2025 — it is thinner, holds less charge and can sit loose against the contacts.

How to Change the Battery

1. Release and remove the emergency blade. Slide the small button/latch on the side of the fob and let the metal key blade flick out, then pull the blade fully free of the housing. On the Tiguan’s folding key this blade also gives you the leverage point for splitting the case.
2. Open the case. With the blade removed you’ll see a slot or seam where the two halves of the housing meet. Insert a flat plastic pry tool (or a small flat-blade screwdriver wrapped in tape to avoid scratches) into the seam and gently twist to pop the two halves apart. It splits along the full edge — work round rather than forcing one spot.
3. Note the orientation, then lift the old cell out. Take a photo or a mental note of which way up it sits before you disturb it.
4. Fit the new CR2032 positive (+) side up — the printed face with the writing points up, toward the buttons, matching the cell you removed. Press it gently until it seats flat under its retaining clip against clean contacts.
5. Close the case. Line up the two halves and press them together all the way round until every clip clicks home — there should be no gap along the seam.
6. Refit the blade by sliding it back into the housing until it latches, then fold it away and test every button.

⚠️ Match the polarity. The positive face goes up on the Tiguan fob; fitting the cell upside down means the key simply won’t transmit, and a cell forced in the wrong way can be flattened. If in any doubt, copy the exact orientation of the cell you took out.

Make Sure It Took

Stand back a few metres and lock, then unlock, the car — full range should return instantly. If a “Key battery low” message was showing, it clears once the car next reads a healthy fob, which can take a drive cycle rather than happening the moment you close the case. On KESSY cars, confirm keyless locking from the door handle and a clean push-button start. If the buttons feel out of step afterwards, simply lock and unlock from the fob while sitting in the car with the doors closed so it re-reads the key.

If a Fresh Cell Doesn’t Fix It

• Re-check polarity and seating. A cell fitted upside down, or one not pressed fully under its clip, is the single most common reason a “new” battery does nothing.
• Wipe the contacts. A smear of finger grease or light corrosion on the terminals is enough to cause dropouts — clean them with a dry cloth before blaming the fob.
• Rule out the car’s 12 V battery. A weak main battery can make the Tiguan slow to wake and mimic key faults. If the fob is fine elsewhere but the car itself is sluggish, the issue is the vehicle, not the key. You can still get in and going with a flat fob — see our guide to starting the Tiguan Mk2 with a dead key fob.

New Key or Spare — Why It’s a Dealer Job

Changing the cell keeps the fob’s existing coding, so nothing needs reprogramming and the key works straight away. A new key is a different matter: the blade has to be cut to the car’s key code, and the transponder and remote must be coded to the Tiguan’s immobiliser with VW-capable diagnostic equipment against the VIN. KESSY keyless fobs are especially tied to the car’s security module. That makes adding a spare or replacing a lost key a job for a VW 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 a VW Tiguan Mk2 key fob take?

One CR2032 3-volt lithium coin cell. The same cell fits both the folding switchblade remote and the KESSY keyless fob on the 2016-onward Tiguan.

Which way up does the battery go?

Positive (+) side up — the lettered face points toward the buttons. Always match the orientation of the cell you removed; fitted the wrong way the key won’t transmit.

Do I need to reprogram the key after changing the battery?

No. Swapping the cell doesn’t affect the fob’s coding, so it pairs to the car exactly as before. Only a brand-new key needs coding to the immobiliser.

How do I open the Tiguan key without breaking it?

Slide the release and pull out the metal emergency blade first, then twist a plastic pry tool in the seam to split the two halves. Removing the blade is what lets the case come apart cleanly.

How long should the fob battery last?

Usually two to three years. Keyless (KESSY) fobs run down a little faster because the key wakes whenever it senses the car, and leaving the fob sitting right next to the car shortens life further.

Can I still drive the Tiguan if the fob is completely dead?

Yes. Use the emergency blade hidden in the fob to unlock the driver’s door, and the keyless system is designed to still start the car when you hold the dead fob against the marked spot — so a flat cell won’t strand you.

If the remote stopped working suddenly — right after the car battery was disconnected, say, rather than fading over weeks — the trigger is more likely a pairing or electrical glitch than a flat cell, and it may leave a stored fault behind. You can look up what any related code means on autodtcs.com.