For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Door Lock/Unlock Signal | 2 | 2 | 2 | --
Door Latch Control | 1 | 1 | 1 | --
Driver Door Lock Switch Ground | -- | 2 | 2 | --
Passenger Front Door Lock Switch Ground | -- | 2 | 2 | --
BCM Ground | -- | 1, 2 | 1, 2 | --
1. Door Lock Malfunction 2. Door Lock Switch Malfunction

### Circuit/System Description

The dr lck fuse supplies battery positive voltage to the body control module (BCM) for the door lock system. The BCM supplies and monitors a reference voltage to the door lock switch through the door lock switch lock/unlock signal circuit. The door lock switch also receives a constant ground source. If a door lock switch is placed in the lock position, the reference voltage is taken directly to ground and the BCM detects the voltage drop on the signal circuit. If a door lock switch is placed in the unlock position, the reference voltage is taken to ground through a 1.5k ohm resistor that is internal to the door lock switches and senses approximately 2.9 volts on the signal circuit. This is how the BCM determines what portion of the door lock switch was activated. The BCM, upon receipt of a door lock switch lock or unlock signal, will switch the appropriate door lock actuator control circuits to battery positive voltage. The opposing side of the door lock actuators are connected to ground internally within the BCM through the other door lock actuator control circuit and the doors will lock or unlock appropriately. Vehicles without keyless entry have 2 internal drivers in the BCM to control the door lock actuators. All door lock and all door unlock. Vehicles equipped with keyless entry have 3 internal drivers in the BCM. Driver door unlock, passenger door unlock and all door lock. This is done to isolate the driver door lock actuator so it can be unlocked by itself using the keyless entry transmitter.

### Reference Information

#### Schematic Reference

Door Lock/Indicator Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Power Door Locks Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the scan tool Door Lock Switch parameter while using the driver and passenger door lock switches. The parameter should change from Idle to Lock and Unlock.

⇒ | If the parameter does not change between the commanded states, refer to Door Lock Switch Malfunction.

2. Command the doors to LOCK and UNLOCK with the scan tool, the door lock actuators should LOCK and UNLOCK when changing between the commanded states.

⇒ | If one or more doors do not LOCK or UNLOCK, refer to Door Lock Malfunction.

### Circuit/System Testing

#### Door Lock Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate door lock switch.
2. Test for less than 1 ohm between the ground circuit terminal A and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Door Lock Switch parameter is Idle.

⇒ | If not the specified value, test the signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal C and ground. Verify the scan tool Door Lock Switch parameters Lock.

⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the door lock switch.

#### Door Lock Malfunction

1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Test for less than 1 ohm between the ground circuit terminal E12 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect the X4 harness connector connector at the BCM and disconnect the harness connector at the appropriate door lock actuator.
4. Test for less than 1 ohm between the control circuit terminal listed below and ground:

• | Driver door lock actuator control circuit terminal 2

• | Driver door lock actuator control circuit terminal 3

• | Passenger door lock actuator control circuit terminal 5

• | Passenger door lock actuator control circuit terminal 6

⇒ | If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

5. Connect a test lamp between the control circuit terminals listed below:

• | Driver door lock actuator control circuit terminal 2 and control circuit terminal 3

• | Passenger door lock actuator control circuit terminal 5 and control circuit terminal 6

6. Ignition ON, command the door latch to LOCK and UNLOCK with a scan tool. The test lamp should briefly illuminate when commanding the LOCK and UNLOCK states.

⇒ | If the test lamp is always OFF, test either control circuit for a short to ground. If the circuits test normal, replace the BCM.

7. If all circuits test normal, test or replace the door lock actuator.

### Component Testing

#### Door Lock Switch Test

1. Ignition OFF, disconnect the harness connector at the appropriate door lock switch.
2. Test for infinite resistance between the signal terminal C and the ground terminal A with the switch in the idle position.

⇒ | If less than the specified value, replace the door lock switch.

3. Test for less than 2 ohms between the signal terminal C and the ground terminal A with the switch in the lock position.

⇒ | If greater than the specified value, replace the door lock switch.

4. Test for 1.4K-1.6K ohms between the signal terminal C and the ground terminal A with the switch in the unlock position.

⇒ | If not within the specified range, replace the door lock switch.

#### Door Lock Actuator

1. Ignition OFF, disconnect the harness connector at the appropriate door lock actuator.
2. Install a 15-amp fused jumper wire between the control terminal 2 and 12 volts. Momentarily install a jumper wire between the control terminal 3 and ground. The door latch should perform the LOCK/ UNLOCK function

⇒ | If the function does not perform as specified, replace the door latch.

3. Reverse the jumper wires; the door latch should perform the UNLOCK/LOCK function.

⇒ | If the function does not perform as specified, replace the door latch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Door Lock Switch Replacement

• | Front Side Door Lock Replacement

• | Control Module References for BCM replacement, setup, and programming