Circuit Description
The following DTC is for the mode actuator.
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 (9.5 to 12 volts). The HVAC control module determines the door 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 to 255 counts.
When a calibration or recalibration procedure is performed, the HVAC control module calculates the door travel range. The HVAC control module commands the actuator to each extreme position and counts the total number of pulses. 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.
Air flow control 3 circuit refers to the mode actuator.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B0248 Air Flow Control 3 Circuit
This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description in Vehicle DTC Information.
DTC Symptom | DTC Symptom Descriptor |
|---|---|
04 | Open Circuit |
51 | Calibration Failure |
61 | Actuator Stuck |
2A | Too Many Pulses |
Conditions for Running the DTC
| • | The ignition is turned ON. |
| • | The ignition voltage is between 9 to 16 volts. |
Conditions for Setting the DTC
B0248 2A and 61
Sets after two occurrences of the test fail code setting conditions listed below in the same ignition cycle.
B0248 51 and 04
Sets after one occurrence of the test fail code setting conditions listed below in the same ignition cycle.
B0248 2A, 04, 51 and 61
The following failures occur and set the DTC:
| • | The HVAC control module does not detect any movement of the actuator |
| • | The HVAC control module detects a measured mode actuator range that exceeds the calibrated value. |
| • | The HVAC control module detects a measured mode actuator range that is less than the calibrated value. |
| • | The HVAC control module detects a calibratible procedure time that exceeds the calibratible value. |
| • | The HVAC control module detects the actuator motor as stalled before the mode actuator motor reaches the expected stall at the end of the travel. When the drive voltage is reversed the motor is unable to move more than a calibrated amount in the other direction. |
| • | The HVAC control module detects the actuator motor as stalled before the mode actuator motor reaches the expected stall at the end of the travel. But, when the drive voltage is reversed the motor is able to move more than a calibrated amount in the other direction. |
Action Taken When the DTC Sets
B0248 2A
The HVAC control module will use a default range to retry calibration procedure when ignition is off.
B0248 61
The HVAC control module will stop trying to move the mode actuator motor during the current ignition cycle.
B0248 04
The HVAC control module will retry the command to move the actuator in a certain direction in 5 minute intervals.
B0248 51
The HVAC control module will retry calibration when ignition is off.
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 40 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 mode actuator. Refer to Air Temperature Actuator Replacement . |
| - | Broken or binding linkages or actuator door |
| - | Obstruction that prevents the 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 mode actuator through its full range of motion.
-
This step verifies the position of the mode actuator.
-
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 Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | ||||||||||
Does the scan tool indicate that the value of the mode Actual parameter changes from the minimum specified value to the maximum specified value? | 0 Counts 255 Counts | Go to Step 3 | Go to Step 4 | |||||||||||
With a scan tool recheck the Mode Door Position parameter in the HVAC control module data list. Does the scan tool display correct values? | -- | Go to Diagnostic Aids | Go to Step 8 | |||||||||||
Does the scan tool indicate that the value of the mode door position parameter position changes by more than the specified value? | 0-3 Counts | Go to Step 8 | Go to Step 5 | |||||||||||
5 | Test the mode door control A circuit and the mode door control B circuit for the following:
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 | ||||||||||
Does the actuator shaft rotate? | -- | Go to Step 10 | Go to Step 7 | |||||||||||
Does the actuator shaft rotate? | -- | Go to Step 10 | Go to Step 8 | |||||||||||
8 | Inspect the mode door and actuator for the following conditions:
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 | ||||||||||
9 | Inspect for poor connections at the harness connector of the mode 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 mode actuator after replacement. Upon fuse replacement a recalibration of the actuator will occur. Replace the mode actuator. Refer to Mode Actuator Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||
12 |
Important: Perform the recalibration procedure for the HVAC control module after replacement. Refer to Actuator Recalibration . Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||
13 |
Does the DTC reset? | -- | Go to Step 3 | System OK | ||||||||||
