Heating & A/C System: 21
21-BLEND DOOR RANGE TOO LARGE
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
NOTE: Diagnose and repair Actuator Circuit Test faults (DTC 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, and 72) before diagnosing Overcurrent faults (DTC 41, 42, 43, and 44) and Calibration faults (DTC 18, 21, 22, 23, 24, 25, 45, 46, 47, 48, 51, 52, 53, 54, 55, and 56). Diagnose and repair Overcurrent faults (DTC 41, 42, 43, and 44) before diagnosing Calibration faults (DTC 18, 21, 22, 23, 24, 25, 45, 46, 47, 48, 51, 52, 53, 54, 55, and 56).
The purpose of actuator calibration is to determine the total span of door travel between physical stops. To calibrate the actuator, the A/C Heater Control first moves the door to its soft stop, and then counts the number of pulses it takes to move the door to its other stop. An expected range of span is stored in the control's memory. If the A/C Heater Control detects too many commutator pulses when calibrating the left blend door, this DTC will set.
- When Monitored:
During actuator calibration.
- Set Condition:
If the A/C Heater Control detects too many commutator pulses when calibrating the left blend door.
1. VERIFY IF ANY ACTUATOR CIRCUIT TEST FAULTS OR OVERCURRENT FAULTS ARE PRESENT
1. Turn the ignition on.
2. Actuate the Clear DTC function by performing the following:
- Turn the blower control on.
- Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.
- When the A/C status indicator begins displaying DTCs, set the Mode switch to the floor position, simultaneously press the A/C mode switch and the EBL mode switch down until both LEDs start flashing (approximately 5 seconds) and then release the mode switches. Stored DTCs will clear from memory in approximately two seconds.
3. Turn the ignition off, wait 10 seconds, and turn the ignition on.
4. Actuate the Actuator Circuit Test / Door Calibration Function by performing the following:
- Turn the blower control off.
- Press and hold the EBL mode switch down and then turn the blower control on. Continue to hold the EBL mode switch down until the EBL status indicator begins flashing. Then, release the EBL mode switch. While the test / function is running, the EBL status indicator will flash once per second. If the test / function passes, the EBL status indicator will stop flashing. If the test / function fails, the A/C and EBL status indicators will flash alternately. Allow the test / function to run to completion before proceeding.
5. Actuate the Display DTC function by performing the following:
- Turn the blower control on.
- Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.
NOTE: The A/C status indicator displays active DTCs when the EBL status indicator is not illuminated and stored DTCs when the EBL status indicator is illuminated.
6. Read DTCs from the A/C status indicator.
Does the A/C status indicator display any of the following DTCs: 41, 42, 43, 44, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, or 72?
Yes
- As present, diagnose and repair the faults in the following order: DTC 72 first, then DTC 62, then DTC 61, then DTCs 64, 66, 68, or 71, then DTCs 63, 65, 67, or 69, and finally DTCs 41, 42, 43, or 44.
No
- Go To 2
2. CHECK FOR A BROKEN LEFT BLEND DOOR ACTUATOR
1. Turn the ignition off.
2. Remove the Left Blend Door Actuator from the A/C Heater Housing Assembly.
3. By hand, attempt to rotate the actuator in both directions.
Does the actuator turn in either direction?
Yes
- Replace the Left Blend Door Actuator.
- Perform the BODY VERIFICATION TEST. Body Verification Test.
No
- Go To 3
3. CHECK THE LEFT BLEND DOOR AND A/C HEATER HOUSING FOR WARPED, WORN, AND DAMAGED COMPONENTS
1. Inspect for excessively worn door linkage and for a damaged or broken A/C Heater Housing Assembly. Inspect for a warped or broken door, and missing door seals. Rotate the door from stop to stop. The door should rotate approximately 90 degrees.
Are there any physical or mechanical problems with the door or housing?
Yes
- Repair as necessary.
- Perform the BODY VERIFICATION TEST. Body Verification Test.
No
- Replace the Left Blend Door Actuator. Then, Go To 4.
4. VERIFY IF THE FAULT IS STILL PRESENT
1. Turn the ignition on.
2. Actuate the Clear DTC function by performing the following:
- Turn the blower control on.
- Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.
- When the A/C status indicator begins displaying DTCs, set the Mode switch to the floor position, simultaneously press the A/C mode switch and the EBL mode switch down until both LEDs start flashing (approximately 5 seconds) and then release the mode switches. Stored DTCs will clear from memory in approximately two seconds.
3. Turn the ignition off, wait 10 seconds, and turn the ignition on.
4. Actuate the Actuator Circuit Test / Door Calibration Function by performing the following:
- Turn the blower control off.
- Press and hold the EBL mode switch down and then turn the blower control on. Continue to hold the EBL mode switch down until the EBL status indicator begins flashing. Then, release the EBL mode switch. While the test / function is running, the EBL status indicator will flash once per second. If the test / function passes, the EBL status indicator will stop flashing. If the test / function fails, the A/C and EBL status indicators will flash alternately. Allow the test / function to run to completion before proceeding.
5. Actuate the Display DTC function by performing the following:
- Turn the blower control on.
- Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.
NOTE: The A/C status indicator displays active DTCs when the EBL status indicator is not illuminated and stored DTCs when the EBL status indicator is illuminated.
6. Read DTCs from the A/C status indicator.
Does the A/C status indicator display DTC 21?
Yes
- Replace the A/C Heater Control.
- Perform the BODY VERIFICATION TEST. Body Verification Test.
No
- Perform the BODY VERIFICATION TEST. Body Verification Test.