Circuit Description
| • | DTC B0248 Mode actuator inoperative |
| • | DTC B0268 Recirculation actuator inoperative |
| • | DTC B0408 Left air temperature actuator inoperative |
| • | DTC B0423 Right air temperature actuator inoperative |
The actuator is an electronic stepper motor. The HVAC control module supplies power and ground to the actuator. The HVAC control module controls the direction of the actuator by changing the polarity of the control circuits. When the actuator reaches its desired position, both circuits are fixed to the same value 0 volts. The HVAC control module determines the door or mode film position by counting pulses, voltage fluctuations, caused by the brush to commutator action generated during normal motor operation. The HVAC control module monitors a voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range of 0-255 counts.
When a calibration or recalibration procedure is performed, the HVAC control module calculates the door or mode film travel range. The HVAC control module commands the actuator in one extreme position then counts pulses starting from 0 counts. The HVAC control module compares the total number of pulses to calibrated limits. If the total pulse count is less than or equal to the maximum calibrated limit and greater than or equal to the minimum calibrated limit, then the calibration is considered successful.
Conditions for Running the DTC
The ignition is turned ON. The inoperative actuator DTC runs during and after the next range check following the setting of the actuator range error DTC. The appropriate actuator inoperative code will set with the appropriate actuator range error code.
| • | DTC B0249 Mode actuator range error |
| • | DTC B0269 Recirculation actuator range error |
| • | DTC B0409 Left air temperature actuator range error |
| • | DTC B0419 Right air temperature actuator range error |
Conditions for Setting the DTC
The HVAC control module does not detect any movement of the actuator.
Action Taken When the DTC Sets
| • | The HVAC control module will recalibrate the appropriate actuator each time the ignition switch is turned ON. |
| • | If DTC B0268 is set, the HVAC control module will command the recirculation door to the outside air position. |
Conditions for Clearing the MIL/DTC
| • | The DTC will become history if the HVAC control module no longer detects a failure. |
| • | The history DTC will clear after 100 fault free ignition cycles. |
| • | The DTC can be cleared with a scan tool. |
Diagnostic Aids
| • | Inspect the actuator door and actuator for the following conditions: |
| - | A misaligned actuator. Refer to Mode Actuator Replacement , Air Temperature Actuator Replacement - Right Side , Air Temperature Actuator Replacement - Left Side or Recirculation Actuator Replacement . |
| - | Broken or binding mode actuator film or actuator door |
| - | Obstruction that prevents the mode film or actuator door from operating within its full range of motion |
| - | Missing seals to the actuator door |
| - | Misaligned seals to the actuator door |
| • | Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies that the HVAC control module is able to command the appropriate actuator through its full range of motion.
-
If the actuator does not move at all, the problem is likely to be the drive circuitry within the HVAC control module, the actuator, or the wiring harness. If the actuator does move, but not within its full range of motion, the problem is likely to be a mechanical binding of the actuator door or actuator door linkage.
-
This step drives the actuator in one position. The actuator shaft will not move if the actuator door is already in the position you are attempting to drive it to.
-
This step drives the actuator in the opposite direction.
Step | Action | Values | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views | ||||||||||||||
1 | Did you perform the Vehicle Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||||
Does the scan tool indicate that the value of the appropriate Actual parameter is within 5 counts or the minimum and maximum specified values? | 3 Counts 250 Counts | Go to Diagnostic Aids | Go to Step 3 | |||||||||||
3 | When commanding the actuator in both directions, does the scan tool indicate that the value of the appropriate Actual parameter changes by more than the specified value? | 3 Counts | Go to Step 7 | Go to Step 4 | ||||||||||
Test the appropriate door control A circuit and the appropriate door control B circuit for an open, high resistance, short to ground or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 5 | |||||||||||
5 |
Does the actuator shaft rotate? | -- | Go to Step 9 | Go to Step 6 | ||||||||||
Does the actuator shaft rotate? | -- | Go to Step 9 | Go to Step 7 | |||||||||||
Inspect the appropriate door and actuator for the following conditions:
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 | |||||||||||
8 | Inspect for poor connections at the harness connector of the appropriate 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 12 | Go to Step 10 | ||||||||||
9 | 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 12 | Go to Step 11 | ||||||||||
10 |
Important: Perform the recalibration procedure for the appropriate actuator. Replace the appropriate actuator. Refer to Mode Actuator Replacement , Air Temperature Actuator Replacement - Right Side , Air Temperature Actuator Replacement - Left Side or Recirculation Actuator Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||||||
11 | Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||||||
12 |
Does the DTC reset? | -- | Go to Step 3 | System OK | ||||||||||
