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HVAC - Automatic




DTC B1405

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 Descriptors

DTC B1405 02
- Control Module Voltage Reference Output 2 Circuit Short to Ground

DTC B1405 05
- Control Module Voltage Reference Output 2 Circuit High Voltage/Open

Diagnostic Fault Information






Circuit/System Description

The Ambient Light/Sunload Sensor integrates the sunload sensor and passenger compartment temperature sensor.

This sensor assembly provides information about:

* Sun heat intensity

* Passenger Compartment Temperature

The solar sensor is connected to ground and to the 5 V stabilized voltage supply through the HVAC Control Module. As the sunload increases, the sensor signal voltage also increases and vice versa. The signal varies between 1.4-4.5 V and is provided to the HVAC Control Module.

The passenger compartment temperature sensor is a negative temperature co-efficient thermistor. A signal and low reference circuit enables the sensor to operate. As the air temperature increases, the sensor resistance decreases. The sensor signal varies between 0-5 V.

This is a bidirectional sensor using a feedback circuit for the HVAC module to send information to the sensor. It is a fault on this feedback circuit that causes this DTC to set.

Bright or high intensity light causes the vehicles interior temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

Conditions for Running the DTC

* Ignition ON

* The HVAC Control Module is ON.

Conditions for Setting the DTC

B1405 02

The input signal is out of range. The voltage is less than 0.1 V.

B1405 05

The input signal is out of range. The voltage is greater than 4.9 V.

Action Taken When the DTC Sets

* The system will use the last valid values as default.

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 Fuel Pump and Level Sensor Assembly

Description and Operation

Automatic HVAC Description and Operation HVAC - Automatic

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 B10B Ambient Light/Sunload Sensor.

2. Test for greater than 10 V between signal circuit terminal 2 and ground.

If less than 10 V

1. Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module.

2. Test for infinite resistance between signal circuit and ground.

If less than infinite resistance, repair the short to ground on the circuit.

If infinite resistance

3. Test for less than 2 ohms in the signal 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 10 V or greater

3. Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module, ignition ON.

4. Test for less than 1 V between the signal circuit terminal 20 and ground.

If 1 V or greater
Repair the short to voltage on the circuit.

If less than 1 V

5. Test or replace the B10B Ambient Light/Sunload Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* HVAC Component Replacement Reference Removal and Replacement

* Control Module References Control Module References for HVAC Control Module programming and setup