Alarm bells

Q My 2002 Toyota Camry 3.0 V6 with the 1MZ-FE engine has been faultless since I got it 10 years and 110,000 miles ago. Recently, however, the factory-fit alarm has been going off every night, then re-setting itself after a minute or so. It doesn’t go off again until the next night, but not at exactly the same time.

The car has no other faults and all other functions work perfectly.

The car is not modified in any way, other than having had a towbar professionally fitted. However, as the alarm fault only started two months later, I’m assuming it’s not related. I did, however, test this by disconnecting the towbar electrics at the fusebox, but it didn’t stop the alarm going off.

I suspect from what I’ve read in online chatrooms that it could be a fault in a sensor that detects a drop in external temperature below a certain level, but

I have no idea which sensor this could be, nor where it is located or how to replace it. Tony Greatorex A There are a few variations of the alarm system – some have an interior radar sensor and/ or a glass sensor – but as far as I can determine none with a temperature sensor. The glass breakage sensor should be located under the dash on the driver’s side and is adjustable.

To determine the cause of the alarm being triggered there is a self-diagnosis test that can be carried out. Before conducting the test it is recommended that the battery terminals are removed and cleaned to ensure a good connection.

The test is carried out as follows:

▶ First, press the ‘unlock’ button on the remote. With the bonnet and boot closed, enter the vehicle, ensuring all doors are now closed.

▶ Place the key into the ignition, but do not turn it. After 5-6 seconds, turn the key to the ‘accessory’ position. Now turn the key to the ‘ignition’ position and back to the ‘accessory’ position five times, ending with the key in the ‘ignition’ position. At no time attempt to start the engine.

▶ The alarm LED should illuminate for nine seconds. While the LED is illuminated, open and close the driver’s door six times, then turn the key back to the ‘accessory’ position. The LED will illuminate for 30 seconds and the indicator lights should flash six times.

▶ While the LED is illuminated, open and close the driver’s door. The indicator lights will flash. You must count the number of times the lamps flash to find the cause of the last triggering of the alarm.

✦ One – Radar sensor

✦ Two – Glass breakage sensor

✦ Three – Door switch

✦ Four – Boot switch

✦ Five – Ignition switch

✦ Six – Vehicle battery cut-lock

(possible low battery)

▶ Now turn the ignition lock from ‘accessory’ to ‘on’ and back to ‘accessory’, the LED will extinguish and the system is reset.