Gremlins ! HA HA HA sorry ! First off a little bit on how they work an what all is involved in making them work ! There are a few control modules in the mix , switches ,relays etc...
Door Lock System Components
The power door lock system consists of the following components:
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The driver door module (DDM)
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The passenger door module (PDM)
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The body control module (BCM)
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The driver information center (DIC)
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The rear door lock switch
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The door lock relay
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The door unlock relay
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The liftgate lock relay--utility vehicles with liftgate only
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The reversible door lock actuators in each of the doors and liftgate
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LOCKS 20A fuse (rear lock/unlock relay supply voltage)
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ECC 10A fuse (liftgate lock relay supply voltage)
Door Lock System Controls
The power door lock system can be controlled by any of the following:
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A power door lock or unlock switch activation
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A keyless entry transmission
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An automatic door lock function
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A delay lock function
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Door lock cylinder switch activation
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Lockout Prevention
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An airbag deployment
The front power door lock switches are integral components of the driver door module (DDM) and passenger door module (PDM). The switches are two position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDM or PDM. The DDM or PDM monitors these inputs and sends a Class 2 message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the Class 2 message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors and liftgate. The rear door lock switch provides a lock and unlock signal to the body control module (BCM). The BCM upon receipt of a lock or unlock signal will control the rear door lock relays and also send a Class 2 message to the DDM and PDM to perform the appropriate function.
The modules which activate the power lock motors are:
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The DDM (driver door lock actuator).
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The PDM (passenger front door lock actuator).
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The BCM (both rear door lock actuators and cargo door/liftgate).
The DDM and PDM are directly connected to the respective door lock actuator through the door lock motor lock and unlock circuits. Once a door lock or unlock request has been received, the module will supply battery voltage to one side of the actuator and ground the other causing the doors to lock or unlock.
The rear passenger and cargo doors differ slightly in that they use lock and unlock relays. The relays supply and coil sides receive a constant voltage through the battery voltage supply circuit. The normally closed contacts are connected to ground and the control side is connected to the BCM. Once a door lock or unlock request has been received by the BCM, the BCM will ground the control side of the appropriate relay. This energizes the relay and allows voltage to be applied to either the door lock motor lock or unlock circuits. since the other side of the door lock actuator is connected to the normally closed contacts of the opposing relay to ground, the doors lock or unlock.
The first place to start is have a factory or equivalent scan tool hooked up , one that can read BCM DTC'S - diagnostic trouble codes ! This could lead to a fix faster ! Watch these three videos !
Door Locks Go Crazy 1
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