B0418

DTC B0408 or B0418

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview






Circuit Description

The HVAC control module commands the air temperature actuator movement with one of 3 voltage signals applied to the air temperature door control circuit. A low voltage of 0 volts moves the air temperature door toward full cold. A voltage of 2.5 volts stops the actuator. A high voltage of 5 volts moves the air temperature door toward full hot. The HVAC control module determines the current position of the actuator by monitoring the feedback voltage of the air temperature door position signal circuit. The feedback potentiometer position is a function of the actuator position. A high voltage indicates a full hot air temperature door position. A low voltage indicates a full cold air temperature door position. The HVAC control module controls the air temperature door position in order to maintain the selected air temperature.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

* DTC B0408 Temperature Control 1 Main Circuit
* DTC B0418 Temperature Control 2 Passenger Circuit

Conditions for Running the DTC

* The ignition is turned ON.
* Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

* The air temperature position signal is less than 5 counts.
* The air temperature position signal is greater than 194 counts.
* The air temperature actuator actual total travel range max-min is less than or greater than the range limits.

Action Taken When the DTC Sets

* The HVAC control module will continue to make use of whatever air temperature actuator travel range is still available.
* The DTC is stored in DTC information.

Conditions for Clearing the DTC

* The DTC will become history if the HVAC control module no longer detects a failure.
* The history DTC will clear after 50 fault-free ignition cycles.
* The DTC can be cleared with a scan tool.

Diagnostic Aids

* A damaged or broken air temperature actuator or mode door can cause this DTC to set.
* If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Diagnostic Aids. Component Tests and General Diagnostics

Test

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Step 10 - Step 15: