The following DTCs are for the HVAC door actuators:
• | B0414 is for the left air temperature actuator. |
• | B0424 is for the right air temperature actuator. |
• | B3761 is for the defrost actuator. |
• | B3770 is for the mode actuator. |
The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of a stepper motor, a logic circuit, and a potentiometer. The potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The module supplies a 5 volt source voltage to the potentiometer on the 5 volt reference circuit. The module supplies ground to the potentiometer through the low reference circuit. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes. The module converts the voltage value to a count value where 1 volt is approximately equal to 51 counts.
The HVAC control module calibrates the travel range of the HVAC door actuators when it is initially powered by the battery positive voltage circuit. During calibration, the module commands the actuators in each direction until door travel is stopped. The module stores the minimum door positions and the maximum door positions of each actuator into memory. The total travel range is calculated by subtracting the minimum door position from the maximum door position. The door actuators can be calibrated again with a scan tool.
• | Battery voltage is 8.7-16.5 volts. |
• | The ignition is ON. |
The DTC sets when one of the following conditions are present:
• | The actual door position value for the actuator is less than 5 counts. |
• | The actual door position value for the actuator is greater than 250 counts. |
• | The actuator fails calibration because the calculated travel range value is too great or too small. |
• | If the DTC sets because the actual door position value is out of range, the HVAC control module will command the actuator to a default position. |
• | If the DTC sets because the actuator failed a calibration, the HVAC control module will attempt to calibrate the motor in the next transition from OFF to RUN mode. |
• | The DTC will become history if the HVAC control module no longer detects the condition that set the DTC. |
• | The history DTC will clear after 100 fault free ignition cycles. |
• | The DTC can be cleared with a scan tool. |
• | If the condition is not present refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
• | If the DTC sets following a calibration of the door actuator, inspect the door and the actuator for the following conditions: |
- | A misaligned actuator |
- | Broken linkages or binding linkages |
- | A broken door or a binding door |
- | An obstruction that prevents the door from operating within the full range of motion |
- | Missing seals to the door |
- | Poor connections at the harness connector of the door actuator |
• | If a signal circuit of an actuator is short to ground and the resistance across the internal potentiometer is low, then this condition could cause a multiple DTC concern. |
The numbers below refer to the step numbers on the diagnostic table.
At least two of the DTC's must be set as current DTC to ensure correct diagnosis. If only one DTC is present then the answer is No.
Tests for the proper operation of the circuit in the low voltage range.
Tests for the proper operation of the circuit in the high voltage range. If the jumper fuse opens when you perform this test, the circuit is shorted to ground.
Tests for a short to voltage in the 5-volt reference circuit.
Tests for a high resistance or for an open in the low reference circuit.
This step tests for an open on the low reference circuit that is common to all of the actuators. Choose the easiest HVAC door actuator that set a DTC to start the diagnosis.
Disconnecting each actuator, one at a time, isolates the disconnected actuators signal circuit from the 5 volt reference circuit that is common to all the actuators.
Step | Action | Values | Yes | No |
---|---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views | ||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | |
2 | Is DTC B1375 set as a current DTC? | -- | Go to Step 3 | |
With a scan tool, observe the Heating and Air Conditioning DTC list. Does the scan tool indicate that at least 2 of the following DTC B0414, B0424, B3761 and B3770 are set as current DTC? | -- | Go to Step 10 | Go to Step 4 | |
4 |
Does the scan tool indicate that the appropriate Door Actual parameter is within the specified range? | 5-250 counts | Go to Step 5 | Go to Step 6 |
5 |
Does the scan tool indicate that the value of the appropriate Door Actual parameter changes? | -- | Go to Diagnostic Aids | Go to Step 19 |
Does the scan tool indicate that the appropriate Door Actual parameter is less than the specified value? | 5 counts | Go to Step 7 | Go to Step 17 | |
Does the scan tool indicate that the appropriate Door Actual parameter is greater than the specified value? | 230 counts | Go to Step 8 | Go to Step 15 | |
Does the voltage measure less than the specified value? | 5.5 V | Go to Step 9 | Go to Step 14 | |
Does the resistance measure less than the specified value? | 5 ohms | Go to Step 22 | Go to Step 18 | |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 18 | |
Did the scan tool indicate that only one DTC was present when a HVAC door actuator was disconnected? | -- | Go to Step 13 | Go to Step 12 | |
12 | Test the 5-volt reference circuit of the appropriate HVAC door actuator for an open. Refer to and to in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 23 |
13 | Test the appropriate door position signal circuit of the HVAC door actuator for a short to ground. Refer to and to in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 22 |
14 | Test the 5-volt reference circuit of the appropriate HVAC door actuator for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 23 |
15 | Test the 5-volt reference circuit of the appropriate HVAC door actuator for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 16 |
16 | Test the door position signal circuit of the appropriate HVAC door actuator for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 23 |
17 | Test the door position signal circuit of the appropriate HVAC door actuator for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 23 |
18 |
Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 23 |
19 |
Does the drive shaft of the appropriate HVAC door actuator rotate? | -- | Go to Step 23 | Go to Step 20 |
20 | Test the door control circuit of the appropriate HVAC door actuator for a short to voltage, for a short to ground, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 21 |
21 | Test the ignition 3 voltage circuit of the appropriate HVAC door actuator for an open or a high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 22 |
22 | Inspect for poor connections at the harness connector of the appropriate HVAC door actuator. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 24 |
23 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 26 | Go to Step 25 |
24 |
Important: Perform the calibration procedure for HVAC door actuators. Replace the HVAC door actuator. Refer to the appropriate replacement procedure: Did you complete the replacement? | -- | Go to Step 26 | -- |
25 | Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 26 | -- |
26 |
Does the DTC set again? | -- | Go to Step 4 | System OK |