Start the Car With a Dead Key Fob Battery

If the remote on your Jeep Wrangler (JL, 2018–Present) has stopped working and the cluster reads “Key Fob Not Detected,” the coin cell inside the fob is the usual cause. The JL’s Keyless Enter-N-Go system has a backup designed for this: a flat fob will still get you into the Wrangler and still start it, because the chip is powered by the vehicle rather than the fob battery. Here is exactly what to do, then how to fit a new cell.

Start the Wrangler with a dead fob battery

There’s a backup RFID reader directly behind the start button that detects the fob’s passive chip at close range:

1. Climb into the driver’s seat, close the door and press the brake pedal firmly.
2. Turn the fob so the nose end — opposite the emergency key blade — faces the dash.
3. Press that nose flat against the ENGINE START/STOP button and hold it.
4. With the fob touching the button, push the button through it. The Wrangler reads the chip and cranks.
5. Once it fires, the fob can go in the cubby for the rest of the drive.

You do not need to pop the start button out of the dash to do this — that forum trick is unnecessary. Holding the fob against the button is the factory method.

Unlock the doors with the emergency key

A dead fob won’t lock or unlock by radio, so use the hidden blade:

1. Find the small release slider on the fob and pull the emergency key blade out of the body.
2. The driver’s door keyhole sits behind a small plastic cap on the handle. Gently pry the cap off with the blade tip or a fingernail.
3. Insert the blade and turn counterclockwise to unlock.
4. Refit the cap and slide the blade back into the fob.

Will the alarm sound?

If the security alarm is armed, opening with the blade may trigger it. Get in and complete the dead-fob start — recognising a valid key clears the alarm.

Replace the key fob battery

The JL fob runs on a single CR2032 3-volt coin cell:

1. Slide the emergency blade out first; the slot it leaves is your pry point.
2. Split the two fob halves with a coin or a small flat screwdriver.
3. Lift out the old CR2032 and fit the new one positive (+) the same way up.
4. Click the halves back together, refit the blade, and test lock/unlock from a few steps away.

Frequently Asked Questions

I can’t see a keyhole on my Wrangler — where is it? It’s under a small cap on the driver’s door handle. Pry the cap off and the cylinder is underneath; it accepts the emergency blade.

Do I keep the fob on the button after it starts? No. The chip is read once at start-up; afterward you can put the fob away.

Nothing lights up when I press the button — is it the fob? No, a completely dark dash means the car’s 12V battery is flat. Jump start the Wrangler first, then retry.

Which battery does the JL fob use? A CR2032 lithium coin cell — keep a spare in the glovebox.

Why does the fob drain so fast? Leaving it within a couple of metres of the parked Wrangler keeps it awake. Store it away from the vehicle overnight to make the cell last.

If a warning light stayed on after the episode, decode it on our sister site autodtcs.com.