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
--- | --- | --- | --- | ---
I/P Fuse Block B+ | 1,2,3 | 1,2,3 | -- | --
Door Unlock Relay Control | B3130 | B3130 | B3130 | --
Driver Door Relay Unlock Control | B3125 | B3125 | B3125 | --
Door Lock Relay Control | B3135 | B3135 | -- | --
Driver Door Lock Switch Lock Signal | B3150 | B3150 | B3150 | --
Driver Door Lock Switch Unlock Signal | B3140 | B3140 | B3140 | --
Passenger Door Lock Switch Lock Signal | B3155 | B3155 | B3155 | --
Passenger Door Lock Switch Unlock Signal | B3145 | B3145 | B3145 | --
Door Lock Switch Ground | -- | 1,2,3 | 1,2,3 | --
I/P Fuse Block Ground | -- | 1,2,3 | 1,2,3 | --
1. Door Locks Inoperative 2. Driver Door Unlock Inoperative 3. Door Unlock Inoperative

### Circuit/System Description

The body control module (BCM) provides battery positive voltage and ground to the appropriate lock and unlock control circuits of the door lock and unlock relays. The lock control circuits of the driver and passenger door latch assemblies share a common relay; however, the unlock control circuits have separate relays. The system is designed this way so that the keyless entry transmitter may be used to unlock only the driver door.

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 or unlock position, the reference voltage is taken directly to ground and the BCM detects 0.0 volts on the signal circuit.

The BCM, upon receipt of a lock switch lock signal, will switch the all lock relay control circuit to battery positive voltage. This will energize the lock relay. The relay will supply voltage to the door lock actuator lock control circuits to one side of the lock actuator. Since the opposing side of the lock actuators are connected to ground through the other lock actuator control circuit and the normally closed contacts of the lock or unlock relay, the doors will then lock appropriately. The remaining unlock relays receive voltage from the underhood fuse block, the BCM upon receipt of a unlock signal or driver door unlock signal will switch the appropriate unlock relay to ground. This will energize the appropriate unlock relay. The relay will supply voltage to the appropriate door unlock control circuits to one side of the appropriate lock actuator. Since the opposing side of the lock actuators are connected to ground through the other lock actuator control circuits and the normally closed contact of the lock relay, the doors will then unlock appropriately.

### Reference Information

#### Schematic Reference

• | Door Lock/Indicator Schematics

• | Release Systems Schematics

#### Connector End View Reference

Vehicle Access Connector End Views

#### Description and Operation

• | Power Door Locks Description and Operation

• | Rear Hatch/Gate Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. Ignition ON, observe the scan tool Driver Door Lock Sw or Psgr Door Lock Sw and Driver Door Unlock Sw or Psgr Door Unlock Sw parameters while pressing and releasing the appropriate door lock switch and door unlock switch. The reading should change between Active and Inactive.

⇒ | If the reading does not change between the specified values, refer to Door Lock Switch Malfunction.

2. Ignition ON, command the driver door and passenger door latches to LOCK and UNLOCK with the scan tool, the doors should LOCK and UNLOCK.

⇒ | If the door latch does not LOCK and UNOCK when changing between commanded states, 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. Ignition OFF, test for less than 1.0 ohm for resistance between the ground circuit terminal C and ground.

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

3. Ignition ON, verify the scan tool Lock Sw parameter is Inactive.

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

4. Verify the scan tool Unlock Sw parameter is Inactive.

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

5. Install a 3 amp fused jumper wire between the signal circuit terminal U and ground. Verify the scan tool Door Unlock Sw parameter is Active.

⇒ | 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.

6. Install a 3 amp fused jumper wire between the signal circuit terminal L and ground. Verify the scan tool Lock Sw parameter is Active.

⇒ | 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.

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

#### Door Lock Malfunction

1. Ignition OFF, disconnect the harness connector C1 at the I/P fuse block.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the ground circuit terminal 25 and ground.

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

3. Ignition OFF, disconnect the harness connector C2 at the I/P fuse block.
4. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 3 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. Ignition OFF, disconnect the harness connector C3 at the I/P fuse block.
6. Connect a test lamp between the control circuit terminal 42 and ground.
7. Ignition ON, command the lock doors ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp does is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

8. Connect a test lamp between the control circuit terminal 8 and B+.
9. Command the driver door unlock ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

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

⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.

10. Connect a test lamp between the control circuit terminal 41 and B+.
11. Command the unlock doors ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

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

⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.

12. Ignition OFF, connect the harness connectors C3, C2 and C1 at the I/P fuse block and disconnect the harness connector at the appropriate door latch.
13. Ignition OFF, test for less than 1.0 ohm of resistance between the control circuit terminal and ground of the appropriate door latch listed below:

• | Driver door latch control circuit terminal 2

• | Driver door latch control circuit terminal 3

• | LR door latch control circuit terminal 2

• | LR door latch control circuit terminal 3

• | RR door latch control circuit terminal 2

• | RR door latch control circuit terminal 3

• | Passenger door latch control circuit terminal 5

• | Passenger door latch 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 circuits test normal, replace the I/P Fuse Block

14. Connect a test lamp between control circuit terminals of the appropriate door latch listed below:

• | Driver door latch control circuit terminal 2 and control circuit terminal 3

• | LR door latch control circuit terminal 2 and control circuit terminal 3

• | RR door latch control circuit terminal 2 and control circuit terminal 3

• | Passenger door latch control circuit terminal 5 and control circuit terminal 6

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

⇒ | If the test lamp remains OFF during either of the commands and the DR/LCK fuse is good, test for a short to ground on both control circuits. If the circuits test normal, replace the I/P fuse block.

⇒ | If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the door latch.

16. If all circuits test normal, test or replace the appropriate door latch.

### Component Testing

#### Door Lock Switch Test

1. Ignition OFF, disconnect the harness connector at the applicable door lock switch.
2. Test for infinite resistance between the signal terminals U and L and the ground terminal C with the switch in the open position.

⇒ | If less than infinite resistance, replace the applicable door lock switch.

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

⇒ | If greater than 2 ohms, replace the applicable door lock switch.

4. Test for less than 2 ohms of resistance between the signal terminal U and the ground terminal C with the switch in the unlock position.

⇒ | If greater than 2 ohms, replace the applicable door lock switch.

#### Driver, LR or RR Door Latch

1. Install a 20A fused jumper wire between the control terminal 3 and 12 volts. Momentarily install a jumper wire between the control terminal 2 and ground.
2. Verify the latch locks.

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

3. Install a 20A fused jumper wire between the control terminal 2 and 12 volts. Momentarily install a jumper wire between the control terminal 3 and ground
4. Verify the latch unlocks.

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

#### Passenger Door Latch

1. Install a 20A fused jumper wire between the control terminal 6 and 12 volts. Momentarily install a jumper wire between the control terminal 5 and ground.
2. Verify the latch locks.

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

3. Install a 20A fused jumper wire between the control terminal 5 and 12 volts. Momentarily install a jumper wire between the control terminal 6 and ground
4. Verify the latch unlocks.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Door Lock Switch Replacement

• | Front Side Door Latch Replacement

• | Rear Side Door Latch Replacement

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