Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Mode Door Control A | 1 | 1 | 1 | -- |
Mode Door Control B | 1 | 1 | 1 | -- |
Mode Door Position Signal A | 1 | 1 | 1 | -- |
Mode Door Position Signal B | 1 | 1 | 1 | -- |
Mode Door Position Signal C | 1 | 1 | 1 | -- |
Mode Door Position Signal D | 1 | 1 | 1 | -- |
Mode Door Position Signal E | 1 | 1 | 1 | -- |
Mode Door Position Signal F | 1 | 1 | 1 | -- |
Mode Actuator Ground | -- | 1 | -- | -- |
1. Air Temperature Actuator Inoperative | ||||
Circuit/System Description
The mode actuator is a 9-wire bi-directional electric motor that incorporates a feedback potentiometers. Ground, 6 position signals, and 2 control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control assembly grounds one of the control circuits while providing the other with 12 volts. The HVAC control assembly reverses the polarity of the control circuits to move the actuator in the opposite direction. As the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 6-8 volts.
Diagnostic Aids
Inspect the mode door and the mode actuator for the following conditions:
| • | A misaligned mode actuator |
| • | Broken or binding linkages or mode door |
| • | An obstruction that prevents the mode door from operating within its full range of motion |
| • | Missing seals to the mode door |
| • | Misaligned seals to the mode door. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the mode actuator.
- Ignition OFF, test for less than 1.0 ohm between the ground circuit terminal J and ground.
- Ignition ON, test for 6-8 volts between ground and the appropriate door position signal circuit terminal listed below:
- Connect a test lamp between control circuit terminal E and control circuit terminal A.
- Command the actuator in both directions by selecting VENT, DEFROST, and VENT with the mode selector switch. The test lamp should turn ON and OFF with each command.
- If all circuits test normal, test or replace mode actuator.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| • | Mode door position signal F terminal C |
| • | Mode door position signal E terminal D |
| • | Mode door position signal D terminal H |
| • | Mode door position signal C terminal B |
| • | Mode door position signal B terminal F |
| • | Mode door position signal A terminal G |
| ⇒ | If greater than the specified range, test the appropriate signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control assembly. |
| ⇒ | If less then specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control assembly. |
| ⇒ | If the test lamp is always ON or always OFF during either of the commands, test both control circuits for a short to voltage, short to ground, or an open/high resistance. If the circuits test normal, replace the HVAC control assembly. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for HVAC control assembly replacement, setup, and programming |
