B1902-77
B1902-77-FRONT MODE DOOR 1 CONTROL - COMMANDED POSITION NOT REACHABLE
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
After the initial installation of the A/C Heater Control, the controller is calibrated to each individual blend/mode door actuator. The actuators are connected to the A/C Heater Control by a dedicated five-wire sensor and control circuits. The actuator can move the blend/mode-air doors in two directions. When the A/C Heater Control pulls the voltage on one side of the control circuit high and the other low, the door actuator will move in one direction. When the A/C Heater Control reverses the polarity of the voltage to the motor, the door actuator moves in the opposite direction. Once the A/C Heater Control makes the voltage to both control circuits high or low, the door actuator will stop its movement and stay in that position. The blend/mode door actuator contains a three wire potentiometer, which the A/C Heater Control uses to monitor the relative position of the blend/mode air doors. The A/C Heater Control learns the blend-air door stop positions during the calibration procedure.
- When Monitored:
Whenever the Mode Door is commanded to move by the A/C Heater Control.
- Set Condition:
The A/C Heater Control monitors the total door movement range. If the door movement is less then or greater than what the controller has stored in its memory, or if the door movement is stalled or stuck, this DTC will set. If the A/C Heater Control detects a valid door movement span in both directions, the DTC will change from Active to Stored and will stay in the controllers memory for 100 ignition cycles.
Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.
1. CHECK FOR RELATED DTCS
1. Ignition on, engine not running.
2. Using the scan tool, read HVAC DTCs.
Are there any Mode Door Actuator Control or Sensor Control DTCs present?
Yes
- Testing and Inspection Perform the appropriate diagnostic procedure.
No
- Go To 2
2. CHECK IF DTC IS ACTIVE
1. Ignition on, engine not running.
2. Using the HVAC controls, switch to all modes from floor, panel and defrost and then back again.
3. Using the scan tool, read HVAC DTCs.
Is this DTC active?
Yes
- Go To 3
No
- Go To 5
3. CHECK THE MODE DOOR
1. Turn the ignition off to the lock position.
2. Remove the Mode Door Actuator and check the Mode Door for binding and full travel. Mode Door Actuator - Removal.
Were there any problems found?
Yes
- Repair or replace the Mode Door as necessary. HVAC Housing - Removal.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.
No
- Go To 4
4. CHECK THE MODE DOOR ACTUATOR
1. Turn the ignition off to the lock position.
2. Replace the Mode Door Actuator. Mode Door Actuator - Removal.
3. Reconnect all previously disconnected connectors.
4. Ignition on, engine not running.
5. Using the scan tool, erase HVAC DTCs.
6. Using the scan tool, perform the HVAC Actuator Calibration Test.
7. Turn the ignition off to the lock position for 30 seconds.
8. Ignition on, engine running.
9. Using the HVAC controls, switch to all modes from floor, panel and defrost and then back again.
10. With the scan tool, read HVAC DTCs.
Did this DTC reset?
Yes
- Replace and program the A/C Heater Control. A/C And Heater Control - Removal.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.
No
- Test complete.
5. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. Using the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
4. Wiggle the wiring and connectors while checking for shorted and open circuits.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.
No
- Test complete.