Circuit Description
The following DTC's are for the HVAC door actuators:
| • | B0234 - left air temperature actuator |
| • | B0249 - mode actuator |
| • | B0269 - recirculation actuator |
| • | B0279 - right air temperature actuator |
The instrument panel module (IPM) controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference, control, 5 volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5 or 5 volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5 volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts. The IPM converts the voltage values to count values where 1 V is approximately equal to 51 counts. The IPM uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, the control signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.
When a calibration or recalibration procedure is performed, the IPM calculates the actuator travel range. The IPM commands the actuator through its full range. The IPM stores the learned minimum and maximum position values. The travel range value is calculated by subtracting the minimum position value from the maximum position value. The IPM compares the travel range to calibrated limits. If the travel range value is less than or equal to the maximum calibrated limit and more than or equal to the minimum calibrated limit, then the calibration is considered successful. The IPM continuously compares the actual actuator position to the calibrated minimum and maximum position values.
Conditions for Running the DTC
| • | The ignition is turned ON. |
| • | The IPM power must be interrupted. |
| • | Perform the Recalibrate all Motors command using the scan tool. |
| • | The IPM will not perform a calibration/recalibration of the mode actuator if DTC B0252 is set as current. |
| • | The IPM will not perform a calibration/recalibration of the recirculation actuator if DTC B0272 is set as current. |
Conditions for Setting the DTC
| • | Left air temperature actuator |
| The actual total travel range of the left air temperature actuator, max-min is less than 152 counts (3.0 volts) or more than 220 counts (4.3 volts). |
| • | Mode actuator |
| The actual total travel range of the mode actuator, max-min is less than 200 counts (3.9 volts) or more than 246 counts (4.8 volts). |
| • | Recirculation actuator |
| The actual total travel range of the recirculation actuator, max-min is less than 149 counts (2.9 volts) or more than 220 counts (4.3 volts). |
| • | Right air temperature actuator |
| The actual total travel range of the right air temperature actuator, max-min is less than 147 counts (2.9 volts) or more than 220 counts (4.3 volts). |
Action Taken When the DTC Sets
| • | Each time the ignition switch is turned ON, the IPM will perform a recalibration of the actuator. |
| • | The IPM will continue to make use of whatever travel range is still available. |
Conditions for Clearing the DTC
| • | The left and right air temperature actuator travel range error must be corrected. |
| • | A successful recalibration of the mode actuator and recirculation actuator must be completed. |
| • | The history DTC will clear after 50 fault-free ignition cycles. |
| • | The DTC can be cleared with a scan tool. |
Diagnostic Aids
| • | If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | A travel range below the actuator specified value suggests an obstruction or something stuck in the door limiting travel. A travel range above the actuator specified value suggests an over travel condition such as damaged or missing foam seal. |
| • | A damaged or broken door an or actuator can cause the DTC to set by allowing the actuator shaft to rotate unrestricted to its internal stop. The internal stops are outside of the working range of the feedback potentiometers 0-250 count. |
Test Description
The numbers below refer to the step numbers on the Diagnostic table.
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Schematics | ||||||||||||||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | |||||||||||||
Does the result of the calculation indicate that the actual travel of the actuator is within the specified range? |
| Go to Diagnostic Aids | Go to Step 3 | |||||||||||||
Test the ignition 3 voltage circuit for an open, high resistance or a short to ground. 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 | |||||||||||||
Test the appropriate door control circuit of the actuator for an open, high resistance, a 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 | |||||||||||||
Test the 5 volt reference circuit for an open, high resistance or a short to ground. 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 | |||||||||||||
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Important: Ensure that the appropriate HVAC actuator connector and the IPM connector are connected during this step in order to avoid misdiagnosis.
Does the actuator drive shaft rotate and do the counts change? | -- | Go to Step 7 | Go to Step 9 | |||||||||||||
Does the voltage measure near the specified value for each commanded state? | 0 V decreasing 5 V increasing 2.5 V stationary | Go to Step 8 | Go to Step 10 | |||||||||||||
8 | Inspect the appropriate HVAC door and the 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 appropriate HVAC 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 IPM. 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 | Replace the HVAC door actuator. Refer to the appropriate replacement procedure: Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||||
12 |
Important: : Perform the Recalibration procedure for the IPM. Replace the IPM. Refer to Instrument Panel 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 | ||||||||||||
