Reset Procedure
SYSTEM TESTSHVAC SYSTEM TEST - ATC AND MTC SYSTEMS
The HVAC System Test, found HVAC - Electrical Diagnostics, provides a starting point in the diagnostic process by identifying the appropriate diagnostic procedure or system test to perform when diagnosing a given symptom, condition, or DTC. It also provides a means for testing the entire HVAC system by utilizing the A/C-heater control's On-Board System Tests. The On-Board System Tests can also assist in diagnosing stored DTCs.
ACTUATOR CALIBRATION - ATC SYSTEM
The Actuator Calibration function homes and repositions the air-door actuators, removes accumulated positioning errors, and checks for air-door span faults. Once actuated, the entire process takes approximately 90 seconds. Upon completion, all air-door actuators should return to the position that the system is currently requesting. Running the Actuator Calibration function is the only way to detect air-door travel too large faults and air-door travel too small faults. These faults, if present, will display on the scan tool after running the Actuator Calibration function.
STARTING ACTUATOR CALIBRATION - ATC SYSTEM
Use a scan tool to start the Actuator Calibration function.
ACTUATOR CALIBRATION - MTC SYSTEM
NOTE: Diagnose and repair Actuator Circuit Test faults (DTC 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, and 72) before diagnosing Overcurrent faults (DTC 41, 42, 43, and 44) and Calibration faults (DTC 18, 21, 22, 23, 24, 25, 45, 46, 47, 48, 51, 52, 53, 54, 55, and 56). Diagnose and repair Overcurrent faults (DTC 41, 42, 43, and 44) before diagnosing Calibration faults (DTC 18, 21, 22, 23, 24, 25, 45, 46, 47, 48, 51, 52, 53, 54, 55, and 56).
The A/C-Heater Control automatically runs the Actuator Calibration function upon ignition on after installing a new A/C-Heater Control. The Actuator Calibration function homes and repositions the air-door actuators, removes accumulated positioning errors, and checks for air-door span faults. Once actuated, the entire process takes approximately 90 seconds. Upon completion, all air-door actuators should return to the position that the system is currently requesting. Running the Actuator Calibration function is the only way to detect air-door travel too large faults, air-door travel too small faults, air-door bound faults, and air-door broken linkage faults. These faults, if present, will display when checking for DTCs in the A/C-heater control.
STARTING ACTUATOR CALIBRATION MANUALLY - MTC SYSTEM
Refer to Starting The Actuator Circuit Test / Door Calibration Function - MTC System.
ACTUATOR CIRCUIT TEST / DOOR CALIBRATION FUNCTION - MTC SYSTEM
NOTE: Diagnose and repair Actuator Circuit Test faults (DTC 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, and 72) before diagnosing Overcurrent faults (DTC 41, 42, 43, and 44) and Calibration faults (DTC 18, 21, 22, 23, 24, 25, 45, 46, 47, 48, 51, 52, 53, 54, 55, and 56). Diagnose and repair Overcurrent faults (DTC 41, 42, 43, and 44) before diagnosing Calibration faults (DTC 18, 21, 22, 23, 24, 25, 45, 46, 47, 48, 51, 52, 53, 54, 55, and 56).
The Actuator Circuit Test / Door Calibration function first tests the air-door electrical circuits for shorts and then it homes and repositions the air-doors to remove accumulated positioning errors and to check for air-door span faults. This test / function supplements the continuous actuator drive system diagnostics and can provide greater detail about shorted air-door electrical circuits by identifying up to three door driver circuits shorted simultaneously. This test will also detect air-door travel too large faults, air-door travel too small faults, air-door bound faults, and air-door broken linkage faults. The Actuator Circuit Test / Door Calibration function must be manually actuated. Faults detected will display when checking for DTCs in the A/C-heater control.
STARTING THE ACTUATOR CIRCUIT TEST / DOOR CALIBRATION FUNCTION - MTC SYSTEM
NOTE: By running the Actuator Circuit Test / Door Calibration Function, the A/C-Heater Control can identify up to three door driver circuits shorted simultaneously. A DTC 72 will set if more than three door driver circuits are shorted in the same direction (e.g. four door driver circuits all shorted to ground) or if two or more door driver circuits are shorted with at least one door driver circuit shorted to ignition and one door driver circuit shorted to ground. To ensure a proper diagnosis, diagnose and repair Actuator Circuit Test faults in the following order: If present, diagnose and repair DTC 72 first, then DTC 62, then DTC 61, then DTCs 64, 66, 68, or 71, and finally DTCs 63, 65, 67, or 69. In addition, always test the door driver circuits after each repair by clearing DTCs, and then running the Actuator Circuit Test / Door Calibration Function, and then checking for DTCs.
To start the Actuator Circuit Test / Door Calibration function for the MTC system, perform the following:
NOTE: An active DTC 34 will prevent the control from performing certain diagnostic functions and it will prevent proper EBL mode switch and status indicator function. If this occurs, diagnose and repair DTC 34 before running the Actuator Circuit Test / Door Calibration function. Refer to HVAC - Electrical Diagnostics for the diagnostic test procedure.
1. Turn the ignition to the On position.
2. Turn the blower motor control (1) to the Off position.
3. Press and hold the EBL mode switch (2) down and then turn the blower motor control on. Continue to hold the EBL mode switch down until the EBL status indicator begins flashing. Then, release the mode switch. While the test / function is running, the EBL status indicator will flash once per second. If the test / function passes, the EBL status indicator will stop flashing. However, if the test / function fails, the A/C and EBL status indicators will flash alternately. Faults detected will display when checking for DTCs in the A/C-heater control.
COOLDOWN TEST - ATC AND MTC SYSTEMS
The Cooldown Test checks A/C system performance by measuring the system's ability to lower the evaporator temperature 11.11° C (20° F) as measured by the evaporator temperature sensor. The following are prerequisites of the Cooldown Test. Verify each of the following before running the Cooldown Test:
- For the ATC system, the Cooldown Test will NOT start if DTC B1031 or B1032 is active. If active, diagnose and repair either DTC before proceeding.
- For the MTC system, the Cooldown Test will NOT start if DTC 31 or 32 is active. If active, diagnose and repair either DTC before proceeding.
- For both systems, verify that the refrigerant system has an adequate charge. Check and repair as necessary before proceeding.
- For both systems, verify that the blower motor operates correctly in all speeds. Diagnose and repair all blower motor related faults before proceeding.
- For both systems, verify that the ambient temperature of the work area is above 18.3° C (65° F) before proceeding. Move the vehicle to a warmer work area if necessary.
- For both systems, verify that the evaporator temperature is above 18.3° C (65° F) before proceeding.
- For both systems, verify that the A/C compressor is NOT running. If the A/C compressor is running, turn the A/C off and allow the evaporator to warm up before proceeding.
STARTING THE COOLDOWN TEST - ATC SYSTEM
Once all of the prerequisites have been met, the Cooldown Test for the ATC system can be actuated by sending a command with a scan tool. Once started, the ATC A/C-heater control automatically sets the blower speed and positions the air-doors for optimal A/C performance. It also sends a request for A/C operation on the CAN B bus. The Cooldown Test can take up to two minutes to run and, will stop running if any of the following occurs:
- The ignition is turned off.
- The A/C compressor is requested off.
- DTC B1031 or B1032 sets during the Cooldown Test.
While the Cooldown Test is running, the A/C status indicator will flash. During this time the A/C-heater control will ignore most of its inputs. If the ATC system passes the test, the A/C status indicator will stop flashing. However, if the ATC system fails the test, both the A/C and EBL status indicators will flash alternately and an active DTC B10B2 will set. The status indicators will continue to flash until either a successful Cooldown Test is executed or until the vehicle is driven a specified number of miles or after 5 ignition cycles. In addition, DTC B10B2 will remain active until a successful Cooldown Test is executed. Always check for DTCs in the A/C-heater control after running the Cooldown Test.
STARTING THE COOLDOWN TEST - MTC SYSTEM
Once all of the prerequisites have been met, the Cooldown Test for the MTC system can be actuated by performing the following:
NOTE: An active DTC 33 will prevent the control from entering diagnostic mode and performing certain diagnostic functions. It will also prevent proper A/C mode switch and status indicator function. If this occurs, refer to A/C HEATER CONTROL WILL NOT ENTER DIAGNOSTIC MODE (MTC) for the diagnostic test procedure. A/C Heater Control Will Not Enter Diagnostic Mode (MTC)
1. Verify that the ignition is in the Off position.
2. Turn the blower motor control (1) to the Off position.
3. Start the engine.
4. Press and hold the A/C mode switch (2) down and then turn the blower motor control to high speed. Continue to hold the A/C mode switch down until the A/C status indicator begins flashing, Then, release the mode switch.
Once actuated, the MTC A/C-heater control automatically positions the air-doors for optimal A/C performance and sends a request for A/C operation to the cluster (CCN) via hardwired circuits. The Cooldown Test can take up to two minutes to run. The test will stop running if any of the following occurs:
- The ignition is turned to the Off position.
- The blower motor control is turned to the any position other than high speed.
- DTC 83 or 84 sets during the Cooldown Test.
While the Cooldown Test is running, the A/C status indicator will flash. During this time the A/C-heater control will ignore most of its inputs. If the MTC system passes the test, the A/C status indicator will stop flashing. However, if the MTC system fails the test, both the A/C and EBL status indicators will flash alternately and an active DTC 35 will set. The status indicators will continue to flash until either a successful Cooldown Test is executed or until the vehicle's ignition on time has exceeded a specified value. In addition, DTC 35 will remain active until a successful Cooldown Test is executed. Always check for and diagnose DTCs present in the A/C-heater control after running the Cooldown Test. If the Cooldown Test fails, service the heating-A/C system as required.