Door Locks: Description and Operation

When a door lock switch is pushed, all doors lock or unlock. Each lock can also be operated manually. The locks are operated by reversible motors that receive voltage from two relays in the Door Lock Relay Assembly. These relays operate the motors by applying battery voltage to one terminal and ground to the other terminal.

When either door lock switch is moved to the LOCK position, it delivers battery voltage to the Door Lock Relay Assembly's LOCK coil. The lock relay is energized. The lock relay contact closes, and battery voltage is applied through the ORN/BLK (60) wire, the closed relay contact, and the GRY (295) wires to the door lock motors. The motors are grounded by the TAN (294) wires through the unlock relay contact to ground. The motor in each door runs to operate the door locks. When the door lock switch is released, the lock relay contact returns to ground and the motors turn off.

A similar action occurs when the unlock relay is energized by either door lock switch closing to the UNLOCK position. Now the TAN (294) wires supply battery voltage to the motors and the GRY (295) wires are grounded. The voltage polarity to the motors has been reversed. The motors run in the opposite direction to unlock the doors.

The door lock switches are usually closed for just a moment. If they are held closed, an electronic circuit breaker in each Motor opens to protect against damage, The circuit breakers have positive temperature coefficients (PTC) and reset automatically when voltage is removed from the motor.

To lock the doors automatically, a momentary battery voltage pulse is applied from the Automatic Door Lock Controller terminal H (lock out) to the Door Lock Relay Assembly's lock relay coil. This is the same way the door lock switches energize the door lock motors when moved to the LOCK position.

Three conditions must be present to allow the controller to lock the doors.

1. No ground at controller terminal E (All doors closed).

2. No battery voltage at controller terminal D (Neutral Safety Backup Switch not in PARK).

3. Ignition Switch in RUN.

The automatic unlock occurs when the Neutral Safety Backup Switch is returned to the PARK position. This provides battery voltage to the controller's park input, terminal D. Momentary battery voltage is then provided from the controller's unlock output, terminal F. This operates the door lock motors in the same way the door lock switches operate the door lock motors when moved to the UNLOCK position.

The Automatic Door Lock Controller also allows the driver to unlock all doors using a key in either front door lock cylinder, see System Check for operation.