Chevrolet Silverado / GMC Sierra. Service manual — part 2349

Recirculation Door Ignition

B0228 02

B0228 05

B0228 05

B0228 61

Recirculation 5-Volt
Reference

B0228 02,
B0413 02,

B0423 02 or

B3779 02

B0228 05

B0228 02,
B0413 02,

B0423 02 or

B3779 02

B0228 61

Recirculation Door Position
Signal

B0228 02

B0228 05

B0228 05

B0228 61

Recirculation Door Control

B0228 02

B0228 05

B0228 05

B0228 61

Recirculation Low
Reference

B0228 02

B0228 05

B0228 05

B0228 61

Driver Air Temperature
Door Ignition

B0413 02

B0413 05

B0413 05

B0413 61

Driver Air Temperature 5-
Volt Reference

B0228 02,
B0413 02,

B0423 02 or

B3779 02

B0413 05

B0228 02,
B0413 02,

B0423 02 or

B3779 02

B0413 61

Driver Air Temperature
Door Position Signal

B0413 02

B0413 05

B0413 05

B0413 61

Driver Air Temperature
Door Control

B0413 02

B0413 05

B0413 05

B0413 61

Driver Air Temperature Low
Reference

B0413 02

B0413 05

B0413 05

B0413 61

Passenger Air Temperature
Door Ignition

B0423 02

B0423 05

B0423 05

B0423 61

Passenger Air Temperature
5-Volt Reference

B0228 02,
B0413 02,

B0423 02 or

B3779 02

B0423 05

B0228 02,
B0413 02,

B0423 02 or

B3779 02

B0423 61

Passenger Air Temperature
Door Position Signal

B0423 02

B0423 05

B0423 05

B0423 61

Passenger Air Temperature
Door Control

B0423 02

B0423 05

B0423 05

B0423 61

Passenger Air Temperature
Low Reference

B0423 02

B0423 05

B0423 05

B0423 61

Mode Door Ignition

B3779 02

B3779 05

B3779 05

B3779 61

Mode 5-Volt Reference

B0228 02,
B0413 02,

B3779 05

B0228 02,
B0413 02,

B3779 61

2008 Chevrolet Silverado 1500

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

Circuit/System Description

The HVAC control module controls the HVAC door actuators to regulate the airflow through the
HVAC system. Each actuator consists of an electric motor and a potentiometer. The module
supplies a low reference and 5-volt reference source voltage to the potentiometer. The HVAC
control module monitors the voltage drop across the potentiometer on the door position signal
circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes.
The control circuit uses either a 0, 2.5 or 5-volt signal to command the actuator movement. When
the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands
the actuator movement in opposite directions.

B0228 is for the recirculate actuator.

B0413 is for the drivers air temperature actuator.

B0423 is for the passenger air temperature actuator.

B3779 is for the mode actuator.

Conditions for Running the DTC

Ignition ON.

The HVAC module is ON.

Conditions for Setting the DTC

The actual door position differs from the commanded door position by more than 4 counts or the
HVAC control module detects the door position signal circuit is less than 3 counts or greater than
253 counts.

Action Taken When the DTC Sets

The control circuit is deactivated for the appropriate actuator.

Conditions for Clearing the DTC

The DTC becomes history when the HVAC control module no longer detects the condition
that set the DTC.

B0423 02 or

B3779 02

B0423 02 or

B3779 02

Mode Door Position Signal

B3779 02

B3779 05

B3779 05

B3779 61

Mode Door Control

B3779 02

B3779 05

B3779 05

B3779 61

Mode Low Reference

B3779 02

B3779 05

B3779 05

B3779 61

2008 Chevrolet Silverado 1500

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

The history DTC will clear after 100 fault-free ignition cycles.

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Air Delivery Description and Operation

Air Temperature 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

Ignition ON, command the appropriate actuator in both directions with a scan tool. The scan tool
door position parameter reading should be between 3 and 253 counts.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate actuator.

2. Test for less than 1 ohm between the low reference circuit terminal 7 and ground.

If greater than the specified range, test the low reference circuit for an open/high
resistance. If the circuit tests normal, replace the HVAC control module.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 10 and

2008 Chevrolet Silverado 1500

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

ground.

If less than the specified range, test the 5-volt reference circuit for a short to ground or
an open/high resistance. If the circuit tests normal, replace the HVAC control module.

If greater than the specified range, test the 5-volt reference circuit for a short to
voltage. If the circuit tests normal, replace the HVAC control module.

4. Verify the appropriate scan tool parameter is less than 4 counts.

If greater than the specified range, test the signal circuit terminal 9 for a short to
ground. If the circuit tests normal, replace the HVAC control module.

5. Install a 3-amp fused jumper wire between the signal circuit terminal 9 and the low

reference circuit terminal. Verify the appropriate scan tool parameter is greater than 250
counts.

If less than the specified range, test the signal circuit for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the HVAC control module.

6. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 5 and

ground.

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

7. Install a DMM between the actuator control circuit terminal 6 and ground. While

monitoring the DMM, use the scan tool to command the appropriate actuator from one
direction to the other. The voltage on the control circuit should move from 0 volts in one
direction to 5 volts in the other direction and 2.5 volts in the at rest state.

If the voltage does not change, test the control circuit for an open, short to voltage or
short to ground. If circuit tests normal replace the HVAC control module.

8. If all circuits test normal, replace the actuator.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Air Temperature Actuator Replacement - Right Side

Air Temperature Actuator Replacement - Left Side

Mode Actuator Replacement

Recirculation Actuator Replacement

DTC P0532 OR P0533

Diagnostic Instructions

2008 Chevrolet Silverado 1500

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