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
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 supplies battery voltage to the variable displacement solenoid valve. When the A/C switch is pressed, the HVAC control module provides a pulse width modulated (PWM) signal to the variable displacement solenoid valve in order to determine the amount of compressor displacement. 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 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 variable displacement solenoid valve is disabled and defaults to the position of lowest possible compressor displacement. The compressor clutch is not disengaged.
B393B 0B
* The variable displacement solenoid valve is disabled and defaults to the position of lowest possible compressor displacement. The compressor clutch is not disengaged.
* 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 Electrical Diagrams
Connector End View Reference
Component Connector End Views A/C Compressor Clutch
Description and Operation
Air Temperature Description and Operation Air Temperature
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 Control Module References 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 1 and control circuit terminal 2.
• 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.
Control Module References Control Module References for HVAC control module replacement, programming and setup