GM Service Manual Online
For 1990-2009 cars only

Models Without Keyless Entry

When either door lock switch is pressed in the power door locks system, all doors lock or unlock in unison. Each lock can also be operated manually from the locking knob.

The locks are operated by reversible actuators that receive voltage from the door lock relay assembly's two built-in relays. The relays energize the actuators by applying voltage to one of the terminals and ground to the other terminal. In order to reverse the actuators, the polarity to the terminals is reversed.

The door lock switches are usually closed briefly. If the door lock switches are held closed, a circuit breaker in each actuator will open to protect against damage. The circuit breaker resets only after voltage is removed from the actuator.

Lock Operation

Pressing the lock position on either door lock switch sends a voltage signal in CKT 195.

Pressing the lock position turns on the lock relay located inside the door lock relay assembly. The lock relay completes the circuit that supplies voltage to CKT 295. CKT 295 is the voltage feed to the actuators.

At this time, the unlock relay is not energized. When the unlock relay is off, CKT 294 is grounded, which provides a ground path to the door lock actuators.

The entire action described completes the electrical circuit the actuators in each door, thus locking the doors.

When the door lock switch is released, the lock relay contact closes to ground, and the actuators turn off.

Unlock Operation

Pressing the unlock position on either door lock switch sends a voltage signal in CKT 194.

Pressing the unlock position turns on the unlock relay located inside the door lock relay assembly. The unlock relay completes the circuit that supplies voltage to CKT 294. CKT 294 is the voltage feed to the actuators.

At this time, the lock relay is not energized. When the lock relay is off, CKT 295 is grounded, which provides a ground path to the door lock actuator.

The entire action described completes the electrical circuit to the actuators in each door, thus unlocking the doors. The polarity of the voltage to the actuators has reversed, causing the actuators to run in the opposite direction in order to unlock the doors.

Models Equipped With Keyless Entry

All door locks operate the same as vehicle models equipped without keyless entry, except the left front door lock.

Lock Operation

Pressing the lock position on either door lock switch sends a voltage signal in CKT 195.

Pressing the lock position turns on the lock relay located inside the door lock relay assembly. The lock relay completes the circuit that supplies voltage to CKT 295. CKT 295 is the voltage feed to the actuators.

At this time, the lock relay is not energized. When the lock relay is off, CKT 295 is grounded, which provides a ground path to all door lock actuators, except left front door lock actuator.

The left front door actuator is grounded through the Remote Control Door Lock Receiver, RCDLR, CKT 694. The RCDLR has a built-in relay. When the built-in relay is de-energized, the relay provides a path to ground to the left front door actuator.

The entire action described completes the electrical circuit to the actuators in each door, thus locking the doors.

When the door lock switch is released, the lock relay contact closes to ground, and the actuators turn off.

Unlock Operation

Pressing the unlock position on either door lock switch sends a voltage signal in CKT 194. The signal is sent to both the unlock relay located inside the door lock relay and the Remote Control Door Lock Receiver, RCDLR.

Pressing the unlock position turns on the unlock relay, and signals the RCDLR to unlock the left front door. the unlock relay completes the circuit that supplies voltage to CKT 294. CKT 294 is the voltage feed to the actuators, except the left front door lock actuator.

The left front door actuator receives voltage through the Remote Control Door Lock Receiver, RCDLR, CKT 694. the RCDLR has a built-in relay. When the built-in relay is energized, the relay provides a voltage to the left front door actuator. The RCDLR energizes the relay when it receives a voltage in CKT 194.

At this time, the lock relay is not energized. When the lock relay is off, CKT 295 is grounded, which provides a ground path to all door lock actuators.

The left front door actuator is grounded through the Remote Control Door Lock Receiver, RCDLR, CKT 694. The RCDLR has a built-in relay. When the built-in relay is de-energized, the relay provides a path to ground the left front door actuator.

The entire action described completes the electrical circuit to the actuators in each door, thus locking the doors.

When the door lock switch is released, the unlock relay contact closes to ground, the RCDLR left door unlock control relay contacts close to ground, and the actuators turn off.