For 1990-2009 cars

### 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 circuit
DTC B393B 0B: Air Conditioning Compressor Valve Control Circuit Current Above Threshold

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
A/C Compressor B+ | B393B 04 | B393B 04 | -- | --
A/C Compressor Control | B393B 04 | B393B 04 | B393B 0B | 1
1. A/C Compressor Malfunction

### 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

#### P393B 04

Measured current is above threshold of 815 mA.

#### P393B 0B

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

### Action Taken When the DTC Sets

#### P393B 04

The A/C compressor is disabled.

#### P393B 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

Manual 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, test for greater than 11 V between the B+ circuit terminal B and ground.

⇒ | If less than the specified range, test the B+ circuit for a short to ground or an open/high resistance.

3. Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module.
4. Ignition ON, test for less than 0.3 V between the control circuit terminal 10 (X2) and ground.

⇒ | If greater than the specified range, test the control circuit for a short to voltage.

5. Ignition OFF, test for infinite resistance between the control circuit terminal 10 (X2) and ground.

⇒ | If less than the specified range, test the control circuit for a short to ground.

6. Test for less than 5 Ω between the Q46 Air Conditioning Compressor Valve control circuit terminal A and control circuit terminal 10 (X2) at the K33 HVAC Control Module harness connector

⇒ | If greater than the specified value, test the control circuit for an open/high resistance.

7. If all circuits test normal, test or replace the Q46 Air Conditioning Compressor Valve and verify the DTC does not reset.

⇒ | If the DTC resets, replace the K33 HVAC Control Module.

### Component Testing

#### Static Test

1. Ignition OFF, disconnect the harness connector at the Q46 Air Conditioning Compressor Valve.
2. Test for 7-10 Ω between control circuit terminal A and B+ circuit terminal B.

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

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

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Air Conditioning Compressor Replacement

• | Control Module References