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DTC B393B

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 04

Air Conditioning Compressor Valve Control Circuit Open

DTC B393B 0B

Air Conditioning Compressor Valve Control Circuit High Current

Circuit/System Description

The HVAC control module supplies battery voltage to the A/C compressor. When the A/C switch is pressed, the HVAC control module provides a pulse width modulation (PWM) signal to the A/C compressor in order to command the performance of the A/C compressor. The performance of the A/C compressor is regulated according to adjusted interior temperature on the basis of characteristic performance data. Therefore the HVAC control module grounds the A/C compressor with the PWM signal.

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 send out 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 Schematics

Connector End View Reference

Component Connector End Views

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 Air Conditioning Compressor Valve.

2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 2 and ground.

3. 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 and the FRT HVAC Fuse circuit open, test or replace the Q46 Air Conditioning Compressor Valve.

4. Verify that a test lamp does not illuminate between the B+ circuit terminal 2 and the control circuit terminal 1.

5. If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the K33 HVAC Control Module.

6. Remove the test lamp.

7. Command the A/C compressor ON with a scan tool. Verify the scan tool A/C Compressor Refrigerant Solenoid Valve Command parameter is 100%.

8. If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the K33 HVAC Control Module.

9. If all circuits test normal, test or replace the Q46 Air Conditioning Compressor Valve.


Component Testing


Static Test

1. Ignition OFF, disconnect the harness connector at the Q46 Air Conditioning Compressor Valve.

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

3. If not within the specified range, replace the Q46 Air Conditioning Compressor Valve.

4. Test for infinite resistance between each terminal and the Q46 Air Conditioning Compressor Valve housing/case.

5. If not the specified value, replace the Q46 Air Conditioning Compressor Valve.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• HVAC Component Replacement Reference

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