Buick Regal: DTC B393B

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 Descriptor

DTC B393B

Air Conditioning Compressor Valve Control Circuit

For symptom byte information, refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

This A/C system uses a conventional clutch to engage and mechanically turn the compressor and a variable displacement solenoid valve to alter the amount of displacement created by the turning of the compressor. The HVAC control module provides both battery voltage and a pulse width modulated ground to the variable displacement solenoid valve. When the A/C switch is pressed, the HVAC control module grounds the variable displacement solenoid using a low side (PWM) signal in order to command the amount of compressor displacement. The performance of the A/C compressor is based on adjusted interior temperature and engine load.

Conditions for Running the DTC

• Ignition ON.
• The HVAC control module is ON.

Conditions for Setting the DTC

B393B 04

A PWM greater than 10% is sent but no current is read back.

B393B 0B

Measured current is above threshold of 815 mA.

Action Taken When the DTC Sets

B393B 04

The A/C compressor is disabled.

B393B 0B

• The A/C compressor is disabled.
• Output will be switched off for hardware protection.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

HVAC Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Automatic HVAC 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 Testing

1. Ignition OFF, disconnect the harness connector at the Q46 A/C Compressor Solenoid Valve.

Connect a test light between terminals 1 and 2 of the harness connector. Ignition ON.

2. Verify the test light turns on and off when commanding the Q46 A/C Compressor Solenoid Valve ON and OFF with the scan tool.

• If the test light does not turn ON and OFF

1. Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module, ignition ON.
2. Test for less than 1 V between ground and each control circuit terminal listed below:
   • terminal 10
   • terminal 11
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Ignition OFF.
4. Test for infinite resistance between ground and each control circuit terminal listed below:
   • terminal 10
   • terminal 11
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
5. Test for less than 2 Ω in each of the control circuits end to end listed below:
   • Q46 A/C Compressor Solenoid Valve terminal 1 and K33 HVAC Control Module terminal 10
   • Q46 A/C Compressor Solenoid Valve terminal 2 and K33 HVAC Control Module terminal 11
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • Go to next step: If less than 2 Ω, replace the K33 HVAC Control Module.

• Go to next step: If the test light turns ON and OFF

3. Test the Q46 A/C Compressor Solenoid Valve or replace the G1 A/C Compressor.

Component Testing

A/C Compressor Solenoid Valve Test

1. Ignition OFF, disconnect the harness connector at the Q46 A/C Compressor Solenoid Valve.

2. Test for 7 - 15 Ω between B+ terminal 2 and control terminal 1.

• If less than 7 Ω or greater than 15 Ω

Replace the G1 A/C Compressor.

• Go to next step: If between 7 - 15 Ω

3. Test for infinite resistance between each terminal and the Q46 A/C Compressor Solenoid Valve housing/case.

• If less than infinite resistance

Replace the G1 A/C Compressor.

• Go to next step: If infinite resistance

4. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• HVAC Component Replacement Reference
• Control Module References for control module replacement, programming and setup

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