Chevrolet Silverado / GMC Sierra. Service manual — part 2354

6. Ignition OFF, connect the X2 harness connector at the blower motor control module.

Disconnect the harness connector at the blower motor.

7. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A and

ground.

If the test lamp does not illuminate, test the B+ circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the blower motor control
module.

8. Connect a test lamp between the control circuit terminal B and the B+ circuit terminal A.

9. Turn the blower motor on high speed then to low speed. The test lamp intensity should be

bright when in high speed and very dim or off when the blower is on low speed.

If the test lamp intensity does not vary, test the control circuit for a short to voltage,
short to ground, or an open/high resistance. If the circuit tests normal, replace the
blower motor control module.

10. If all circuits test normal, test or replace the blower motor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Blower Motor Control Module Replacement

Blower Motor Replacement

Control Module References for ECM, and HVAC control module setup, replacement, and
programming

ACTUATOR RECALIBRATION

When replacing the HVAC control module it will be necessary to allow the HVAC control
module to perform a calibration process. When installing the HVAC control module be sure to
perform the following:

1. Place the ignition switch to the OFF position.

2. Disconnect the scan tool.

3. Install the HVAC control module.

4. Connect all previously disconnected components.

IMPORTANT: Do not adjust any controls on the HVAC control module while the

HVAC control module is self-calibrating. If interrupted, improper
HVAC performance will result.

2008 Chevrolet Silverado 1500

2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

5. Start the vehicle.

6. Wait 40 seconds for the HVAC control module to self-calibrate.

7. Verify that no DTCs have set as current DTCs.

When replacing the HVAC actuator it will be necessary to allow the HVAC control module to
perform a calibration process. When installing the HVAC actuator be sure to perform one of the
following:

Preferred Method (w/ Scan Tool)

1. Clear all DTCs.

2. Place the ignition switch in the OFF position.

3. Install the HVAC actuator.

4. Connect all previously disconnected components.

5. Start the vehicle.

6. With the scan tool, initiate the Motor Re-calibration feature of the Heating and Air

Conditioning Special Functions menu.

7. Verify that no DTCs have set as current DTCs.

Alternate Method (w/o Scan Tool)

1. Clear all DTCs.

2. Place the ignition switch to the OFF position.

3. Install the HVAC actuator.

4. Connect all previously disconnected components.

5. Remove the HVAC/ECAS fuse for a minimum of 10 seconds.

6. Install the HVAC/ECAS fuse.

7. Start the vehicle.

IMPORTANT: Do not adjust any controls on the HVAC control module while the

HVAC control module is self-calibrating. If interrupted, improper
HVAC performance will result.

IMPORTANT: Do not adjust any controls on the HVAC control module while the

HVAC control module is self-calibrating. If interrupted, improper
HVAC performance will result.

2008 Chevrolet Silverado 1500

2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

8. Wait 40 seconds for the HVAC control module to self-calibrate.

9. Verify that no DTCs have set as current DTCs.

REPAIR INSTRUCTIONS

HVAC CONTROL MODULE REPLACEMENT

Fig. 4: View Of HVAC Control Assembly & Screws
Courtesy of GENERAL MOTORS CORP.

Callout

Component Name

Preliminary Procedure

1. Remove the instrument panel accessory trim plate. Refer to Instrument Panel

Accessory Trim Plate Replacement (without RPO SLT) or Instrument Panel
Accessory Trim Plate Replacement (with RPO SLT) .

2. Remove the accessory switch assembly. Refer to Accessory Switch Replacement

(with RPO SLT) or Accessory Switch Replacement (without RPO SLT) .

3. Disconnect the electrical connectors.

Screw, Control Assembly - Heater and Air Conditioning (Qty: 2)

NOTE:

2008 Chevrolet Silverado 1500

2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

AIR TEMPERATURE ACTUATOR REPLACEMENT - LEFT SIDE

Fig. 5: View Of Air Temp Actuator & Screws
Courtesy of GENERAL MOTORS CORP.

1

Tighten: 1.5 N.m (13 lb in)

Refer to Fastener Notice .

2

Control Assembly, Heater and Air Conditioning
Tip: HVAC Control Module must be reprogrammed. Refer to Control
Module References .

Callout

Component Name

Preliminary Procedure

1. Remove the instrument panel to the service position. Refer to Instrument Panel

NOTE:

In order to avoid actuator damage, DO NOT apply power to the actuator when it is not installed in
the HVAC module.

2008 Chevrolet Silverado 1500

2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado