GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 G8 🢒 DTC 🢒 DTC B3125, B3130, or B3135

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.

DTC Descriptors

DTC B3125 00: Left Front/Driver Door Only Unlock Circuit

DTC B3130 00: All Door Unlock Circuit

DTC B3135 00: All Door Lock Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

I/P Fuse Block B+

1

1

1

--

Door Lock Switch Lock Signal

B3150 00

2

2

--

Door Lock Switch Unlock Signal

B3140 00

2

2

--

All Lock Relay Control

B3135 00

B3135 00

1

--

Door Latch Assembly Control

1

1

1

--

Driver Unlock Relay Control

B3125 00

B3125 00

B3125 00

--

Pass Unlock Relay Control

B3130 00

B3130 00

B3130 00

--

Master Window Switch Ground

--

2

2

--

Relay Ground

--

1

1

--

1. Door Lock Malfunction

2. Door Lock Switch Malfunction

Circuit/System Description

The body control module (BCM) controls the door lock, passenger door unlock and driver door unlock relays. Voltage is applied to the appropriate relay through the door lock/unlock control circuit when the BCM detects a door lock/unlock switch activation or a keyless entry lock or unlock command.

Conditions for Running the DTC

The system voltage is 9-16 volts.

Conditions for Setting the DTC

B3125 00

The BCM detects a fault on the DRVR DR/UNLCK relay control circuit.

B3130 00

The BCM detects a fault on the PASS DR/UNLCK relay control circuit.

B3135 00

The BCM detects a fault on the DR/LCK relay control circuit.

Action Taken When the DTC Sets

The power door locks will malfunction.

Conditions for Clearing the DTC
    • The DTC will be current for as long as the fault is present.
    • When the fault is no longer present, the DTC will become a history DTC.
    • A history DTC will clear after 50 ignition cycles.

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

Command the Driver Door Unlock, Lock Rear Doors and Unlock Rear Doors with the scan tool, all doors should perform the LOCK and UNLOCK function.

⇒If B3125 00 is set, refer to DRVR DR/UNLCK Relay Control Malfunction.
⇒If B3130 00 is set, refer to PASS DR/UNLCK Relay Control Malfunction.
⇒If B3135 00 is set, refer to DR/LCK Relay Control Malfunction.

Circuit/System Testing

DRVR DR/UNLCK Relay Control Malfunction

  1. Ignition OFF, disconnect the DRVR DR/UNLCK relay.
  2. Connect a test lamp between the control circuit terminal 85 and the B+ circuit terminal 86.
  3. Ignition ON, command the Driver Door Unlock with a scan tool. The test lamp should briefly illuminate when commanding the UNLOCK state.
    4. ⇒If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
    ⇒If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, test or replace the DRVR DR/UNLCK relay.

PASS DR/UNLCK Relay Control Malfunction

  1. Ignition OFF, disconnect the PASS DR/UNLCK relay.
  2. Connect a test lamp between the control circuit terminal 85 and the B+ circuit terminal 86.
  3. Ignition ON, command the Unlock Rear Doors with a scan tool. The test lamp should briefly illuminate when commanding the UNLOCK state.
    4. ⇒If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
    ⇒If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, test or replace the PASS DR/UNLCK relay.

DR/LCK Relay Control Malfunction

  1. Ignition OFF, disconnect the DR/LCK relay.
  2. Connect a test lamp between the control circuit terminal 85 and the ground circuit terminal 86.
  3. Ignition ON, command the Lock Rear Doors with a scan tool. The test lamp should briefly illuminate when commanding the LOCK state.
    4. ⇒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.
    ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, test or replace the DR/LCK relay.

Component Testing
  1. Ignition OFF, disconnect the appropriate relay.
  2. Test for 60 - 200 Ω between terminals 85 and 86.
    3. ⇒If not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals:
    4. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    ⇒If less than the specified value, replace the relay.
  4. Test for less than 2 Ω between terminals 30 and 87A.
    5. ⇒If greater than the specified range, replace the relay.
  5. Install a 3A fused jumper wire between relay terminal 85 and 12V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.
    6. ⇒If greater than specified range, replace the relay

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Control Module References for BCM replacement, setup and programming