B104D

B104D-BLEND DOOR CONTROL CIRCUIT LOW





For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.

Theory of Operation

After the initial installation of the Front A/C Heater Module, the controller is calibrated to each individual blend/mode door actuator. These calibrations are stored as in the number of pulses it takes to move the door from one stop to another. The Front A/C Heater Module drives the Door Actuators by the use of Door Driver circuit and a Common Door Driver circuit and monitors all door actuator pulses to detect door movement in both directions. Most of the door actuators share a common door driver circuit but each door actuator has its own unique driver circuit. Due to shared circuitry, similar DTCs can set at the same time for multiple actuators depending upon the type of circuit malfunction, its location, and the direction the actuator is moving when the malfunction is present.

- When Monitored:
With the ignition on and a HVAC Actuator DTC Detection Test is performed.

- Set Condition:
If a HVAC Actuator DTC Detection Test is performed and the Front A/C Heater Module detects a short to ground condition for the period of five seconds. If another HVAC Actuator DTC Detection Test is performed and the Front A/C Heater Module detects a valid current draw, 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 IF DTC IS ACTIVE
1. Ignition on, engine not running.
2. With the scan tool, erase HVAC DTCs and perform the HVAC Actuator DTC Detection Test.

Did this DTC reset?

Yes

- Go To 2

No

- Go To 4

2. CHECK THE (C61) FRONT BLEND DOOR DRIVER CIRCUIT FOR A SHORT TO GROUND




1. Turn the ignition off to the lock position.
2. Disconnect the Front A/C Heater Module C1 harness connector.
3. Disconnect the Left Front Blend Door Actuator harness connector.
4. Measure the resistance between ground and the (C61) Front Blend Door Driver circuit.

Is the resistance below 100k Ohms?

Yes

- Repair the (C61) Front Blend Door Driver circuit for a short to ground.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 3

3. CHECK THE LEFT FRONT BLEND DOOR ACTUATOR AND FRONT A/C HEATER MODULE
1. Replace the Left Front Blend Door Actuator.
2. With the scan tool, erase HVAC DTCs and perform the HVAC Actuator DTC Detection Test.

Did this DTC reset?

Yes

- Replace and program the Front A/C Heater Module.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Test complete.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

4. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. With the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
4. Check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, partially broken wires.
5. Check the connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals.
6. 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.