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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8594
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I've got a 2002 Montero and the horn and alarm goes off by

Customer Question

Customer: ***** *****, I've got a 2002 Montero and the horn and alarm goes off by itself. what could be the problem?
JA: Thanks. Can you give me any more details about your issue?
Customer: It just happened Monday morning about 3 a.m. the alarm just went off by itself and would stop until I removed the fuse. Then this morning at the same time the horn started blowing by itself, so I started the car the banged the horn a few times, then it went off. Mind you, it's about 19 degrees where I am so that may be the issue, but it's never happened before. ***** *****
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Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.


It is most likely that you are hearing the actual horn short and not the alarm. This is a common complaint on this vehicle as it ages (And other Mitsubishis of this era). If the horn sound is one long tone, then the horn is shorted and the alarm is not involved. This happens from the switch inside the air bag failing over time; it uses a membrane contact switch that eventually begins passing continuity particularly in cold weather (The membrane swells/contracts with weather changes).
You can confirm this 100% by taking the access panel off the bottom of the steering wheel, locating the single horn wire (not the two-wire connector, that is for the air bag) and unplugging the bullet connector on the single wire. The problem goes away, you know for sure it is the horn switch (air bag assembly).

Once confirmed.... a new air bag is the only way to correct it back to original condition, Mitsubishi does not sell service parts for it (As they don't want anyone taking apart the air bags). Of course if you don't have safety inspections there is no harm in leaving it unplugged either, you just won't have a horn.

If the horn is honking repeatedly, then it would be an alarm issue.... and at that there are only two real considerations.... either a small voltage draw somewhere (The alarm is tripped by voltage fluctuations) or a remote that is failing (when they fail they oftne send random "panic" signals to the vehicle). To rule the latter out, jsut take the batteries out of all your remotes and see if it stops. If it does you know you have a bad remote. If it does not, then a more in depth hands on diagnosis would be necessary to see what is causing a draw on the system.