DTC B0413, B0423, B3761, or B3773. Buick Lucerne 2007

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2007 🢒 Lucerne 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B0413, B0423, B3761, or B3773

Circuit Description

The HVAC control module controls the HVAC actuators to regulate the airflow through the HVAC system. Each actuator is a 2-wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction.

The HVAC control module determines the door position by counting motor pulses on one of the control circuits. The HVAC control module converts the pulses to counts with a range of 0-255 counts.

When a calibration or recalibration procedure is performed, the HVAC control module calculates the door travel range. The HVAC control module compares the total number of pulses to calibrated limits. If the total pulse count is less than or equal to the maximum calibrated limited and more that or equal to the minimum calibrated limit, then the calibration is considered successful.

•	Air Flow Control 3 Circuit refers to the mode actuator.

•	Air Flow Control 7 Circuit refers to the recirculation actuator.

•	Temperature Control 1 Circuit refers to the driver temperature actuator.

•	Temperature Control 2 Circuit refers to the passenger temperature actuator.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

•	DTC B0413 06 Temperature Control 1 Feedback Circuit Short to Ground or Open

•	DTC B0423 06 Temperature Control 2 Feedback Circuit Short to Ground or Open

•	DTC B3761 06 Airflow Control 3 Feedback Circuit Short to Ground or Open

•	DTC B3773 06 Airflow Control 7 Feedback Circuit Short to Ground or Open

Conditions for Running the DTC

The HVAC control module has completed a calibration/recalibration of the actuator.

Conditions for Setting the DTC

The HVAC control module does not detect any movement of the actuator, after 2 unsuccessful attempts at moving the actuator.

Action Taken When the DTC Sets

The HVAC control module will recalibrate the appropriate actuator each time the ignition switch is turned ON.

Conditions for Clearing the DTC

•	The DTC will become history if the HVAC control module no longer detects a failure.

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

•	The DTC can be cleared with a scan tool.

Diagnostic Aids

Inspect the appropriate actuator door and actuator for the following conditions:

•	A misaligned actuator

•	Broken or binding linkages or actuator door

•	Obstruction that prevents the actuator door from operating within its full range of motion

•	Missing seals to the actuator door

•	Misaligned seals to the actuator door

Test Description

The numbers below refer to the step numbers on the diagnostic table.

This step drives the actuator in one direction. The actuator shaft will not move if the actuator door is already in the position you are attempting to drive it to.

This step drives the actuator in the opposite direction.

Step

Action

Yes

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

Test the appropriate door control A circuit and the appropriate door control B circuit for an open, high resistance, short to ground, or a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 3

Turn OFF the ignition.
Disconnect the HVAC control module.
Connect a 10-amp fused jumper wire between the actuator door control A circuit of the appropriate actuator and battery positive voltage.
Connect a 10-amp fused jumper wire between the actuator door control B circuit of the appropriate actuator and a good ground.

Does the actuator shaft rotate?

Go to Step 7

Go to Step 4

Connect a 10-amp fused jumper wire between the actuator door control B circuit of the appropriate actuator and battery positive voltage.
Connect a 10-amp fused jumper wire between the actuator door control A circuit of the appropriate actuator and a good ground.

Does the actuator shaft rotate?

Go to Step 7

Go to Step 5

Inspect the appropriate door and actuator for the following conditions:

•	A misaligned actuator

•	Broken or binding linkages or actuator door

•	An obstruction that prevents the actuator door from operating within its full range of motion

•	Missing seals to the actuator door

•	Misaligned seals to the actuator door

Did you find and correct the condition?

Go to Step 10

Go to Step 6

Inspect for poor connections at the harness connector of the appropriate actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 8

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 9

Important: Perform the recalibration procedure for the appropriate actuator.

Replace the appropriate actuator. Refer to Temperature Valve Actuator Replacement Mode Actuator Replacement or Recirculation Actuator Replacement .

Did you complete the replacement?

Go to Step 10

Replace the HVAC control module. Refer to HVAC Control Module Programming and Setup for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 10

Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK