DTC 1 - Mode Actuator Did Not Reach Defrost Position

DIAGNOSTIC TROUBLE CODE 1 - MODE ACTUATOR DID NOT REACH "DEFROST" POSITION
When the HVAC Control Module calibrates the Mode Door Actuator, it first moves the actuator toward the DEFROST position. In the DEFROST position, circuit C37 of the 21 pin connector should have a value of approximately 0.3 to 0.8 volts. When the actuator does not reach the DEFROST position, DTC 1 sets.

Detection
When the voltage at C37 is approximately 2 volts or greater, the DRB III will display the DTC.

Possible Causes
- Mode Door reaches the DEFROST position and does not respond to changes in the control panel settings.
- Mode Door Feedback Signal circuit is OPEN.
- Mode Door Feedback Signal circuit is SHORTED to 5 or 12 volts.
- Mode Door is stuck.
- Mode Door Actuator is stuck.
- Mode Door Driver circuit is OPEN.
- Mode Door Driver Circuit is SHORTED to ground. Diagnostics begin momentarily and then STOP with no LED's until the short is removed, and then both WIPE and INTERMITTENT LED's flash simultaneously.
- Mode Door Actuator gear is not properly connected.
- Sensor ground circuit OPEN may set multiple DTC's 1, 4, 5, and 8, and defaults to Full Hot and Defrost. Recirc continues to operate.

If there is air flow in the Defrost position, even though the DTC indicates that the actuator cannot reach the Defrost position, there is and open in the Mode Door Feedback Signal circuit (the door is moved to the Defrost position attempting to lower the feedback voltage).

If the Mode Door Actuator fails between Bi-Level and Mix, both DTC's 1 and 2 will be set.

If the Mode Door Actuator fails in the Panel Position and is blowing air in this position, DTC 1 is set.

Test Procedures
Disconnect the Actuator connector.
1. Using a voltmeter, measure between pins 1 and 5. If the voltage is not 12 volts ± 1 volt, check the actuator driver circuits wiring for a short or open circuit. Measure the voltage between pins 2 and 4. If the voltage is less than 4 volts, check the 5 volt supply circuit. Measure the voltage between pins 3 and 4.If the voltage is less than 4.5 volts, check the actuator feedback circuit.
2. Remove actuator, and check if the gear pins are in the correct track on cam or if they are binding. If OK, go to Step 3. If not OK, repair as necessary.
3. Check for binding door, if door is binding repair as necessary If gears and door are OK, replace actuator.
4. Once repairs are completed repeat the Calibration Diagnostic and Cooldown test. Repeating the test is necessary to clear the fault codes.