Power door lock system – general information
1. The power door lock system operates the power door motors, which are integral components of the door latch units in each door. The system consists of a fuse (in the engine compartment fuse and relay box), the instrument cluster, the control switches (in each of the front doors), the power door motors and the electrical wiring harnesses connecting all of these components.
2. The lock mechanisms in the door latch units are actuated by a reversible electric motor in each door. When you push the door lock switch to LOCK, the motor operates one way and locks the latch mechanism. When you push the door lock switch the other way, to the UNLOCK position, the motor operates in the other direction, unlocking the latch mechanism. Because the motors and lock mechanisms are an integral part of the door latch units, they cannot be repaired. If a door lock motor or lock mechanism fails, replace the door latch unit (see Body).
3. Even if you don’t manually lock the doors or press the door lock switch to the LOCK position before driving, the instrument cluster automatically locks the doors when the vehicle speed exceeds 15 mph, as long as all the doors are closed and the accelerator pedal is depressed. You can turn off this feature if you don’t want the doors to lock automatically. Refer to your owner’s manual.
4. Some vehicles have an optional Remote Keyless Entry (RKE) system that allows you to lock and unlock the doors from outside the vehicle. The RKE system consists of the transmitter (the electronic push-button key) and a receiver located on the instrument cluster. The RKE receiver, which operates all the time, is protected by a fuse in the engine compartment fuse and relay box. Vehicles are shipped from the factory with two RKE transmitters but, if you want to purchase extra units, the RKE receiver can actually handle up to four vehicle access codes.
5. Some features of the door lock system on these vehicles rely on resources that they share with other electronic modules through the Programmable Communications Interface (PCI) data bus network. Proper diagnosis of these modules and the PCI data bus network requires the use of a DRB III (proprietary factory) scan tool and factory diagnostic information. At-home repairs are therefore limited to inspecting the wiring for bad connections and for minor faults that can be easily repaired. If you are unable to locate the trouble using the following general steps, consult your dealer service department.
6. Always check the circuit fuses (in the engine compartment fuse and relay box) first.
7. When depressed, each power door lock switch locks or unlocks all of the doors. The easiest way to verify that each door lock switch is operating correctly is to watch the door lock button in each door as you operate the switch. The door lock buttons should all go down when you push the door lock switch to the LOCK position, and go up when you push the door lock switch to the UNLOCK position. Also, with the engine turned off so that you can hear better, operate the door lock switches in both directions and listen for the faint click of the motors locking and unlocking the latch mechanisms.
8. If there’s no click, check for voltage at the switches. If no voltage is present, check the wiring between the fuse and the switches for shorts and opens (see the wiring diagrams at the end of this chapter).
9. If voltage is present, but no clicking sound is apparent, remove the switch from the door trim panel (see Body) and test it for continuity. If there is no continuity in either direction, replace the switch.
10. If the switch has continuity but the latch mechanism doesn’t click, check the wiring between the switch and the motor in the latch mechanism for continuity. If the circuit is open between the switch and the motor, repair the wiring.
11. If all but one motors is operating, remove the trim panel from the affected door (see Body) and check for voltage at the motor while operating the lock switch. One of the wires should have voltage in the LOCK position; the other should have voltage in the UNLOCK position.
12. If the inoperative motor is receiving voltage, replace the latch mechanism.
13. If the inoperative motor isn’t receiving voltage, check for an open or short in the circuit between the switch and the motor. Note: It’s common for wires to break in the harness between the body and the door because repeatedly opening and closing the door fatigues and eventually breaks the wires.