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 Descriptors

DTC B0403 61: Rear Climate Control Selection Switch Assembly Circuit signal invalid

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Rear Blower Motor Speed Control Signal | B0408 61 | B0408 61 | B0408 61 | --
Rear Temperature Selector Control Signal | B0408 61 | B0408 61 | B0408 61 | --
Rear Mode Door Control Signal | B0408 61 | B0408 61 | B0408 61 | --

### Circuit Description

The Rear HVAC Control is a 5 wire control module, Low reference, 5 volt reference and signal circuits enable the control circuits to operate. The temperature and mode actuator signal varies between 0 and 5 volts. The HVAC control module converts the signal to a range between 0 and 255 counts. The rear auxiliry blower motor is pulse width modulated and gives a scan tool reading of 0-100 percent blower speed.

The following DTC is for the control circuit between the front HVAC Control Module and the Rear HVAC Control Module. This DTC monitors the rear mode door control, rear temperature selector control, and the rear blower motor speed control circuits.

• | DTC B0403 61 is for the rear mode actuator door control circuit.

• | DTC B0403 61 is for the rear temperature actuator selector control circuit.

• | DTC B0403 61 is for the rear blower motor speed control circuit.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

#### Rear Temperature Actuator Potentiometer out of Range

The HVAC control module detects the signal circuit is less than 12 counts or more than 246 counts.

#### Rear Blower Potentiometer out of Range

The HVAC control module detects the signal circuit is less than 5 counts or more than 250 counts. 0 to 100 percent blower speed.

#### Rear Mode Potentiometer out of Range

The HVAC control module detects the signal circuit is less than 5 counts or more than 250 counts.

### Action Taken When the DTC Sets

The driver information center (DIC) will display SERVICE A/C SYSTEM.

### Conditions for Clearing the DTC

• | The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.

• | The history DTC will clear after 100 fault-free ignition cycles.

### Reference Information

#### Schematic Reference

HVAC Schematics

#### Connector End View Reference

HVAC Connector End Views

#### Description and Operation

• | Air Temperature Description and Operation

• | Air Delivery 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 Verification

Ignition ON, observe the appropriate mode or temperature door . Select the full hot setting then the full cold temperature setting at the rear HVAC control head. The scan tool aux temp door reading should transition between 12 and 246 counts. Select the various mode door settings at the rear HVAC control. The scan tool aux mode door reading should transition between 5 and 250 counts.

Ignition ON, Command the auxiliary blower motor speed from OFF to Full Blower speed on the Rear HVAC control, observe the scan tool aux blower motor pulse width modulated (PWM) percentage. The percentage should mirror the rear hvac control head selection going from 0 to 100 percent in blower speed.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the Rear HVAC Control.
2. Test for less than 10 ohms of resistance between the low reference circuit terminal 5 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance.

3. Ignition ON, test for 4.8-5.2 volts between the low reference circuit terminal 4 and the appropriate signal circuit terminal .

• | Rear blower motor speed control circuit terminal 7.

• | Rear temperature selector control circuit terminal 8.

• | Rear mode door control circuit terminal 10.

⇒ | If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the Rear HVAC control module.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the Rear HVAC control module.

4. If all circuits test normal, test or replace the Rear HVAC control.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Auxiliary Heater and Air Conditioning Control Replacement