Circuit Description
The HVAC control module commands the left air temperature actuator movement with one of three voltage signals applied to the left air temperature door control circuit. A low voltage of 0 volts moves the left air temperature door toward full cold. A voltage of 2.5 volts stops the door. A voltage of 5 volts moves the left air temperature door toward full hot. The HVAC control module determines the current position of the actuator by monitoring the feedback voltage of the left air temperature door position signal circuit. The feedback potentiometer position is a function of the actuator position. A high voltage indicates a full cold left air temperature door position. A low voltage indicates a full hot left air temperature door position. The HVAC control module controls the left air temperature door position in order to maintain the selected air temperature.
Whenever the HVAC control module keep alive memory battery power is interrupted, the HVAC control module will perform a recalibration of the actuators. During recalibration, the HVAC control module will drive the actuators to their minimum and maximum travel extremes. The HVAC control module will then calculate a travel range from this data and compare it to a calibrated range within the HVAC control module. If the actual travel range is not within the calibrated expected range, the actuator will be considered not calibrated and the DTC will set.
Conditions for Running the DTC
| • | The ignition is turned ON. |
| • | The HVAC control module power must be interrupted. |
Conditions for Setting the DTC
The left air temperature actuator actual total travel range is less than or greater than the calibrated limits.
Action Taken When the DTC Sets
| • | The HVAC control module will continue to make use of whatever left air temperature actuator travel range is still available. |
| • | Each time the ignition switch is turned ON the HVAC control module will perform a recalibration of the actuator. |
Conditions for Clearing the DTC
The left air temperature actuator travel range error must be corrected.
Diagnostic Aids
| • | The range fault code can only be detected following a check of the left air temperature actuator travel range. The left air temperature actuator travel range check can only be initiated by disrupting power to the HVAC control module (disconnecting the battery) or with the scan tool. |
| • | The calibration limit is 147 - 220 counts (2.9-4.4 V). An actual range below this limit suggests an obstruction, something stuck in the door limiting travel. An actual range above this limit suggests an over travel condition, damaged or missing foam seals. |
| • | If condition not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Step | Action | Values | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Schematics | ||||||||||||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | |||||||||||
2 |
Does the result of the calculation indicate that the actual travel of the left air temperature actuator is within the specified range? | 147-220 counts | Go to Diagnostic Aids | Go to Step 3 | ||||||||||
3 | Test the ignition 3 voltage circuit of the left air temperature actuator for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 4 | ||||||||||
4 | Test the air temperature door control circuit of the left air temperature actuator for an open, high resistance, short to ground or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 5 | ||||||||||
5 | Test the 5 volt reference circuit of the left air temperature actuator for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 6 | ||||||||||
6 |
Important: The left air temperature actuator connector and the HVAC control module connector must be connected to correctly perform test.
Does the left air temperature actuator drive shaft rotate and do the counts change? | -- | Go to Step 7 | Go to Step 9 | ||||||||||
7 |
Does the voltage measure near the specified value when increasing temperature, near the specified value when decreasing temperature and near the specified value when stationary? | 0V decreasing 5V increasing 2.5V stationary | Go to Step 8 | Go to Step 10 | ||||||||||
8 | Inspect the left air temperature door and the left air temperature actuator for the following conditions:
Did you find and correct the condition? | -- | Go to Step 13 | Go to Diagnostic Aids | ||||||||||
9 | Inspect for poor connections at the harness connector of the left air temperature actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||||||||
10 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||||||||
11 |
Important: Perform the recalibration procedure for the left air temperature actuator. Replace the left air temperature actuator. Refer to Air Temperature Actuator Replacement - Left Side . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||
12 |
Important : Perform the recalibration procedure for the HVAC control module. Replace the HVAC control module. Refer to HVAC Control Module Replacement in Body Control System. Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||
13 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||||||
