Q: 2012 toyota highlander limited: Alarm often goes off without reason, even when I am in the car with the keys.

asked by on January 12, 2018

The car's alarm often goes off often without reason. For example, sometimes I would get in the car with the keys, and just before turning on the car, the alarm would go off and I have to hit the panic button to stop it. Other times, I would have the car parked in the garage at home with the doors unlocked, and when I try to open the door the alarm would go off, unless I have the key with me. This means, even when at home with the car safely parked in my locked garage, I have to carry the key with me even if I just want to pick up something from the car. I took the car to the Toyota dealership, and apparently they did not see anything wrong and did not do much to try to find out. One technician there speculated that it could be a faulty "after-market" alarm system (I bought the car used...). Please help. Thanks.

My car has 60000 miles.
My car has an automatic transmission.

Load test the vehicle battery. Sometimes when a battery is on the verge of failure, the resulting voltage drop "fools" the vehicle alarm system as this voltage drop is interpreted by the computer as tampering. If the battery passes the load test but only marginally (be sure to get the specific test results and compare to new battery specs) replace the battery outright. Apart from this, there is a diagnostic decision tree in the factory service manual that covers these sorts of failures. A mechanic has to go through the decision tree, line by line, to pinpoint the fault. If the issue is not the battery, the recommended service to diagnose and resolve this is an electrical circuit/component diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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