Chevrolet Silverado / GMC Sierra. Manual

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Verification

1. Verify that the BCM door lock switch parameters display Idle, Lock, and Unlock while

operating the driver and passenger door lock switches to lock and unlock.

If either of the scan tool parameters do not match the actual switch positions perform
the Door Lock Switch Circuit Test.

2. Verify that a test lamp connected to ground illuminates on the supply side of the lock fuses 1

and 2 when a lock switch is activated.

If the test lamp does not illuminate at one or both fuses perform the Door Lock Relay
Control Circuit Test.

If the test lamp illuminates at both fuses perform the Door Lock Actuator Circuit Test.

3. Verify that a test lamp connected to ground illuminates on the supply side of the unlock

DRV fuse when an unlock switch is activated.

If the test lamp does not illuminate at any of the fuses perform the Driver Door Unlock
Relay Control Circuit Test.

If the test lamp illuminates perform the Door Lock Actuator Circuit Test.

4. Verify that a test lamp connected to ground illuminates on the supply side of the unlock

fuses 1 and 2 when a unlock switch is activated.

If the test lamp does not illuminate at one or both fuses perform the Door Lock Relay
Control Circuit Test.

If the test lamp illuminates at both fuses perform the Door Lock Actuator Circuit Test.

Circuit/System Testing

Door Lock Switch Circuit Test

1. Disconnect the affected door lock switch and verify that the scan tool switch parameter

displays Idle.

If the parameter displayed is Lock or Unlock test the affected switch signal circuit for
a short to ground. If the circuit tests normal replace the BCM.

2. Verify less than 1 ohm or resistance from the ground circuit terminal B to ground.

If the resistance is greater than the specified value repair the ground circuit for an
open/high resistance.

3. Connect a fused jumper wire from the lock switch signal circuit terminal D to ground and

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Vehicle Access - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

verify that the scan tool switch parameter displays Lock.

If the parameter displayed is not Lock test the lock switch signal circuit for an
open/high resistance. If the circuit tests normal replace the BCM.

4. Connect a fused jumper wire from the unlock switch signal circuit terminal E to ground and

verify that the scan tool switch parameter displays Unlock.

If the parameter displayed is not Unlock test the unlock switch signal circuit for an
open/high resistance. If the circuit tests normal replace the BCM.

5. If the circuits test normal replace the affected door lock switch.

Door Lock Relay Control Circuit Test

1. Verify that a test lamp connected to battery voltage illuminates when connected to the

supply side of the lock 1 and 2 fuses in the IP fuse block.

If the test lamp does not illuminate test the lock/unlock relay ground circuit for an
open/high resistance. If the circuit tests normal replace the IP fuse block.

2. Disconnect the BCM connector X7.

3. Verify that all of the door lock actuators lock when a fused jumper wire is connected to the

door lock relay control circuit terminal 7 and briefly applied to battery voltage.

If all of the door lock actuators do not lock, test the door lock relay control circuit for
an open/high resistance. If the circuit tests normal replace the IP fuse block.

If only the front or rear door lock actuators do not lock replace the IP fuse block.

4. If the circuits test normal replace the BCM.

Driver Door Unlock Relay Control Circuit Test

1. Verify that a test lamp connected to battery voltage illuminates when connected to the

supply side of the DRV unlock fuse in the IP fuse block.

If the test lamp does not illuminate test the IP fuse block ground circuit for an
open/high resistance. If the circuit tests normal replace the IP fuse block.

2. Disconnect the BCM connector X7.

3. Verify that the driver door lock actuator unlocks when a fused jumper wire is connected to

the driver door unlock relay control circuit terminal 6 and briefly applied to ground.

If the driver door lock actuator does not unlock, test the driver door unlock relay
control circuit for an open/high resistance. If the circuit tests normal replace the IP
fuse block.

4. If the circuits test normal replace the BCM.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Vehicle Access - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Passenger Door Unlock Relay Control Circuit Test

1. Verify that a test lamp connected to battery voltage illuminates when connected to the

supply side of the unlock 1 and 2 fuses in the IP fuse block.

If the test lamp does not illuminate test the IP fuse block ground circuit for an
open/high resistance. If the circuit tests normal replace the IP fuse block.

2. Disconnect the BCM connector X7.

3. Verify that all of the passenger door lock actuators unlock when a fused jumper wire is

connected to the passenger door unlock relay control circuit terminal 9 and briefly applied
to ground.

If the passenger door lock actuators do not unlock, test the passenger door unlock
relay control circuit for an open/high resistance. If the circuit tests normal replace the
IP fuse block.

4. If the circuits test normal replace the BCM.

Door Lock Actuator Circuit Test

1. Disconnect the affected door latch connector and connect a test lamp across the lock

actuator control circuit terminals.

2. Verify that the test lamp illuminates briefly when a lock and unlock switch is activated.

If the test lamp does not illuminate in both switch positions test the lock actuator
control circuits for an open/high resistance or short to ground. If the circuits test
normal replace the IP fuse block.

3. If the circuits test normal replace the affected door latch.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Front Side Door Lock Replacement

Rear Door Lock Replacement (Extended Cab Upper) or Rear Door Lock
Replacement (Crew Cab) or Rear Door Lock Replacement (Extended Cab Lower)

Instrument Panel Electrical Center or Junction Block Replacement - Left Side

Control Module References for BCM replacement, programming, and setup

POWER DOOR LOCKS INOPERATIVE - REAR

Diagnostic Instructions

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Vehicle Access - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

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.

Circuit/System Description

The driver and passenger door lock and side window switches are integrated control module
switch assemblies. The DDS and PDS door lock switches are normally open, 2 position rocker
type switches, with detents for lock and unlock. The DDS and PDS are directly connected to the
respective door lock actuator through the door lock actuator control circuits. When a door lock
or unlock function is activated from the DDS or PDS a GMLAN lock or unlock command is sent
to the other door switch and body control module (BCM). The BCM controls the rear door lock
actuators through a printed circuit board relay in the IP fuse block. The unlock side of the relay is
controlled by the BCM through a low side drive control circuit and the lock side of the relay is
controlled through a high side drive control circuit. When the BCM grounds the door unlock
control circuit, the unlock relay coil is energized and battery voltage is supplied to the unlock
actuator control circuits through the unlock fuses 1 and 2. During unlock operation the actuators
are grounded through the lock control circuits to the lock fuses 1 and 2 and the de-energized lock
side of the relay. When the BCM supplies voltage the lock relay control circuit, the lock relay
coil is energized and battery voltage is supplied to the lock actuator control circuits through the
lock fuses 1 and 2. During lock operation the actuators are grounded through the unlock control
circuits to the unlock fuses 1 and 2 and the de-energized unlock side of the relay.

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

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Vehicle Access - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

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Chevrolet Silverado / GMC Sierra. Manual - part 1538