B393B
DTC B393B
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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
Diagnostic Fault Information
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 lines. 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 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 Schematics HVAC - Automatic
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
Automatic HVAC Description and Operation Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Programming and Relearning for scan tool information
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the Q46 A/C compressor solenoid valve. It may take up to 2 minutes for all vehicle systems to power down.
2. Verify a test lamp illuminates between the B+ circuit terminal 2 and ground.
• If the test lamp does not illuminate
1. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance.
2. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K33 HVAC control module.
• If the test lamp illuminates
3. Ignition ON, connect a test lamp between the control circuit terminal 1 and the B+ circuit terminal 2.
4. Verify the test lamp turns ON and OFF when commanding the A/C Compressor Refrigerant Solenoid Valve ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module, ignition ON.
2. Test for less than 1 V between the control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Ignition OFF.
4. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K33 HVAC control module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K33 HVAC control module.
• If the test lamp turns ON and OFF
5. Test or replace the Q46 A/C compressor solenoid valve.
Component Testing
Static Test
1. Ignition OFF, disconnect the harness connector at the Q46 Air Conditioning Compressor Valve.
2. Test for 7-15 ohms between B+ circuit terminal 2 and control circuit terminal 1.
• If less than 7 ohms or greater than 15 ohms
Replace the Q46 Air Conditioning Compressor Valve
• If between 7-15 ohms
3. Test for infinite resistance between each terminal and the Q46 Air Conditioning Compressor Valve housing/case.
• If less than infinite resistance
Replace the Q46 Air Conditioning Compressor Valve
• If infinite resistance
4. All OK
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* HVAC Component Replacement Reference HVAC Component Replacement Reference
* Control Module References Programming and Relearning for HVAC control module replacement, programming, and setup.