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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8598
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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2002 mitsubishi diamante: keyless entry..unlock..the locking mechanism

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My 2002 mitsubishi diamante has started to relock the doors when i use the keyless entry controls. Also when i unlock the car, the time i open the door the alarm goes off. the easiest way to shut the alarm off is to lock the doors again. i've looked at the locking mechanism's in both front doors and they look fine and seem to be functioning correctly. I'm starting to consider finding a way to disable the alarm system in the car "if Possible". Any guidance on this would be appreciated.

With the remote battery being new and eliminated as a possibility, what has most likely happened here is you have either a failed lock cylinder switch, or a damaged wire in the door opening pass-through.

When the vehicle is told to unlock the doors, it checks continuity across numerous points in the system, and if an abnormality is found, it returns to previous condition (locked). The most common cause for this is the lock cylinder switch falling off or jamming. You can verify this by putting the key into the lock cylinder and turning it each direction; if it is working normally, it will lock and unlock all doors on two turns. If it does not lock all doors or does not unlock all doors (or both), there is a problem with the switch; check both switches (2002 *should* have a passenger door cylinder... if yours is already a drivers side only car, disregard).
If both switches are installed and working the next likely suspect is a damaged wire where the harnesses pass through from the body of the car to each door. These get brittle and break from years of opening/closing. You would want to check and double check all functions you can for each door to look for other possible symptoms to help narrow down the location further.

You can not disable the alarm in this car; the core of the alarm is run off the ETACs computer, which incorporates your locks, interior lighting, windshield wipers, etc into one unit; disabling it would render a large portion of the car useless because of this.

If I had to bet, I would wager the drivers door cylinder switch is either fallen off or the wiring to it is broken.
Customer: replied 6 years ago.
So after checking the key in the door lock method. I've found that the passenger door unlocks all doors and locks all doors. the driver side unlocks only the driver side door (but locks after i remove the key from the door). so the next step would be to take the door panel off and remove the door cylinder? is this done by just removing the screws and wiring from the cyclinder?
Yes, the next step is to remove the door panel and check the lock cylinder switch. The lock cylinder switch is like a "hat" that sits on the back of the lock cylinder and rotates when you turn the cylinder with the key.

For your description now I would be nearly 100% that you have a bad or fallen off lock cylinder switch on the driver side... and very close second would be damaged wires, but the switches fail more often (they often fall off entirely).

You will need to remove the door panel and pull back the plastic weather sheeting, and the lock cylinder should be just barely visible in th e upper rear corner; you will want to look for the switch attached to the back, make sure it is securely attached... it will likely be fallen off entirely or crooked (half popped off). If it is firmly installed, follow the wiring down from it (it has about a 8 inch pigtail) to make sure the wiring didn't get caught in the glass and sever.
If everything looks OK still, pop the switch of the cylinder (gently pry it off) and use a flat edge screwdriver to rotate the center of the switch and see if you get feedback from the lock/alarm system... if you do not, either the switch is faulty or the wiring is damaged in the door pass through or similar... further diagnosis would require a ohm meter to test the switch.
Customer: replied 6 years ago.
okay, the switch was found in place: i removed the connection at the end of the 8 inch wire header. you mentioned that i could check it with a multimeter for correct functionality? Also after i connected it back in, the door seemed to work better. the main issue is this thing has been an intermittent problem over the last few months. so if there was method to stress test the switch to confirm repair. if it is the switch should i locate a dealer for the switch or ebay/internet it?
It may have just been a bit loose on the cylinder or loose at the harness if the condition improved after checking it.

You can check the switch with an ohm meter, however be aware if you have an intermittent fault it may test OK but fail at another time.
To test it, set your multimeter to Ohms and connect one lead to pin 2 .
With the other lead connected to pin 1 you should have continuity only when turning the key toward UNlock. With the other lead connected to pin 3 you should have continuity only when turning the key toward LOCK.

If you do not have full continuity in these two positions (or if you have partial continuity in other positions than indicated), the switch is failed.

Knowing that the problem comes and goes, it still would be a good idea to check the wiring where it passes through the door for broken or brittle wires.

If you do need the switch, it runs about $35 and can be purchased separately from the cylinder. It is a dealer-only part, so you will need to source one from either a local dealer, an internet dealer, or a used part provider. I recommend Mentor Mitsubishi as they typically sell for about 25% below retail (though the difference may not compensate for shipping on this inexpensive of a part).
Customer: replied 6 years ago.

I noticed that there is a pretty hefty rubber boot on the wiring location between door and body of the car. i've contemplated pulling one end out to check wiring but was a little nervous of the stress it would cause in the wiring bundle.


I checked conitinuity and it is functioning correctly, in the lock position it read around 7 ohms, unlock seemed to be slightly less. i noticed with the wiring disconnected the keyless entry seemed to function correctly. probably due to the bad connection being the issue.

That is actually not the best reading... it may be your meter, but you should show 0.000 when positioned in one of the test positions... there should be zero resistance when the key is turned in the proper direction being tested. This would be enough to cause an issue.

Yes you can leave it unplugged and your problem will technically go away, however you would have to use your passenger door lock cylinder to disarm the alarm... as turning the key in the drivers door will no longer cancel the alarm since the switch is disconnected.

You can push the wiring through the door opening for a better inspection... it should unplug just inside the body of the car, then the harness can be pushed into the duct and through to the door frame, then remove the speaker for access to the harness for inspection. Be aware though that the fit through that duct is very tight for the connector to fit through... it will fit, it just isn't a lot of fun.
Doug and 3 other Mitsubishi Specialists are ready to help you
Customer: replied 6 years ago.
my multimeter line shorted together reads about .2 ohms so maybe i should pull the switch off and inspect it or just replace it. thanks for the guidance on this. i appreciate your efforts
It sounds pretty solid like a bad switch... while the .2 reading is a lot better than 7 ohms, I would still lean heavily toward a bad switch, especially if disconnecting it corrects the issue. You can inspect the wiring still, I would probably just go ahead with the switch though seeing as it isn't too much money.

If you need any further help with this, just let me know I'd be glad to help.
Customer: replied 6 years ago.
great thanks again. it's nice being able to talk to someone who knows about this stuff. if i change the switch out and still have issues. i'll check the wiring harness
No problem at all, I'm glad to help. Keep me posted, if necessary.
Have a great day!

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