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LionheartUK 12-29-2012 12:43 PM

2002 WJ alarm issue after dead battery

I wanted to share an issue I recently had with my 02 WJ (UK 2.7 CRD).

Having tried to start it one morning the battery was flat so it barely turned over and the alarm siren chirped a few beeps. I took the battery off to charge it but my charger said it was only operating at 40% capacity.

With this in mind I left it off and decided to buy a new battery the following day.

I installed the new battery and pressed the unlock button on the keyfob, the doors unlocked with 2 "beeps" from the alarm siren..

Odd I thought, but got in put the keys in the ignition and turned the key to ON, waiting for the glow plugs to warm the alarm started chirping high speed morse code, "uh oh" (in Homers voice) I thought, but proceeded to start the car without issue, the morse code continued!

I switched off and hit the forums, all advice to no avail, resetting alarm actively/passively, battery off for 30 minutes then on with doors shut etc. etc.

I was about to admit defeat and take it to a dealership......

Then my wife stated that perhaps something needed "energising" after the flat battery - BINGO! the Alarm has an internal battery that is only used when the main battery is disconnected, but once flat only charges when the engine is running. (info pulled from the service manual section VEHICLE THEFT SECURITY 8Q - 13)

So the cure is : Leave the engine running enduring the morse code until the battery has enough charge in it and stops all by itself. I would recommend leaving it running to add more charge before switching off.

Frango100 12-29-2012 06:47 PM

Re: 2002 WJ alarm issue after dead battery
Yes, that is a good one. Your jeep must have the premium alarm system installed, which has ultrasonic sensors inside the cabin, but also a separate siren module with a backup battery. I had seen a problem like this before, but never heard about the solution. Good to know in case others come up with this.
I donīt think they sold this premium alarm in the US.

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