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sprinkles08, ASE Certified Technician
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Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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toyota Yaris S: yaris with intermittent doors loclin/unlocking.

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yaris with intermittent doors loclin/unlocking. Initially 3 doors only were operating, now only two. Different doors unlock on different occasions. It is as if there is a relay with burnt contacts sending signals to only 2 solenoids at a time. If so, where is this relay located
Hello and welcome to JustAnswer!

The door lock actuators are controlled directly by the body control module (BCM) so there aren't any relays used.

There are a few possible causes and it will most likely take some electrical testing to determine what is happening.

You can try disconnecting the battery for a minute or so, reconnect it and see if that restores operation at all. It's possible that the BCM could be seeing current draw going too high on one of the lock or unlock circuits and is disabling operation. Disconnecting the battery may restore operation temporarily if that's the case.

If that doesn't help then some testing will need to be done. The problem could be the BCM itself, a wiring issue between the BCM and the lock actuators, or the actuators themselves which are integral to the door latches.

When you open the doors you will see a black rubber boot going between the door and body, this is where the wiring harness runs from the main harness into the door. This wiring flexes each time the door is open and closed and wires can eventually break. If the problem is intermittent it may be happening because of broken wiring that is making intermittent contact. What you would need to do is remove the trim panel from a door that's acting up and use a test light to check for power and ground while pressing the lock switch. If you find that power or ground is missing at a latch when testing then the next place to go would be looking in the boot for damaged wiring.

If you do find power and ground are ok yet it won't lock or unlock then the actuator has failed and the latch will need to be replaced.
Customer: replied 3 years ago.

Hi sprinkles08


Thanks for the answer, I found it pretty helpful. I can stop looking for the relay now!

Hoping you can steer me towards wether it is a wire issue, BCM or door actuator.I put a voltmeter on the plug to the driver door actuator and got varying levels, seemingly with door position, ranging from .5V to 11.5V. I was able to get consitent volt readings above 10V in a certain door position, when I re-plugged the door actuator wiring (whilst depressing door open switch) I was unable to ever get the door actuator to fire open or close. (does this mean that door actuator is definetly failed, or should I confirm by running a wire direct to actuator to check operation?) However, both the remote (on the key) and hard switch (on door console would only open or close 2 doors (back right and front left, no activity on other 2). After about 8 lock and unlock repeats, no doors would open/close. I disconnected battery briefly, after which front left and rear left doors open and close OK. Does this point to a faulty BCM, since I had not touched any doors, other than driver's door (front right), meaning that any dodgy wiring had not been disturbed. If I can get the drivers door actuator to fire with bridging wire straight from battery, do I look for faulty wire in that door rubber boot or is it the BCM? The fact that the system only does 2 doors, but varies between rear left and rear right, does this mean faulty BCM or can a faulty wire and or door actuator cause the BCM to operate intermittently as described?


It sounds like you've proven the actuator on the driver's door is bad for sure. If it was getting power and ground but the actuator wasn't doing anything then it has failed. It's failure could be causing the BCM to disable the lock and unlock drivers because of high current draw, which explains why the others came back with the battery disconnect.
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Customer: replied 3 years ago.

Thanks for that, happy with service. Will rate to finish

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