Manual A/C Systems

Diagnostic Trouble Codes (DTC's)
The Manual A/C system is controlled by the Body Control Module (BCM). The system can be diagnosed by the DRB scan tool or the vehicles own control head display. Refer to Displaying and Reading Trouble Codes for checking Diagnostic Trouble Codes (DTC's). Note that there are two DTC tables. The ATC and Manual A/C DTC table contain faults that are common to both the ATC and the Manual A/C system. The same diagnosis can be used for both systems. The DTC's cover operation of the climate control unit actuators, doors, evaporator temperature sensor, ambient temperature sensor and the A/C refrigerant system. The Manual A/C DTC table covers Fault Codes that are for the manual A/C Control Head and wiring.

ATC And Manual A/C DTC'S:

Manual A/C DTC'S:

Manual A/C Control Head:

Trouble Codes From The Manual A/C Control
The trouble codes can be checked with the Manual A/C control and the Odometer Display of the Mechanical Instrument Cluster of a DRB scan tool is not available. The Manual A/C Control Head can only be placed into the diagnostic mode while the engine is running and the vehicle is not moving. To place the system into it's diagnostic mode, adjust the Manual A/C Control to the following settings:
1. The engine must be running with vehicle not moving.
2. The Fan Speed set to any speed except OFF.
3. The Temperature Knob in full cold (full counterclockwise position).
4. The mode knob must be placed in defrost position (full clockwise position).
5. The A/C button can be ON or OFF.
6. Press and hold the Rear Defrost button until the Mechanical Instrument Cluster Odometer display indicates an "AC00". The body control module (BCM) will chime once and the Manual A/C control A/C button LED will begin blinking.

Manual A/C Control Head:

7. Release the Rear Defrost button and wait until the Manual A/C Control A/C button LED stops blinking. This means that the error check and climate control unit door calibration is complete.

Diagnostic trouble codes related to the Manual A/C Control and the climate control unit will appear on the odometer display in numerical form after the letters "AC". The diagnostic trouble codes are stored in the BCM and can range between 23 and 51.The odometer display will return to normal operation if no trouble codes are found. If a problem is found, then the odometer will display the letters "A/C" followed by the trouble code number. The odometer display can only show one diagnostic trouble code at a time. Under certain circumstances, more than one diagnostic trouble code could be in the memory To scroll through any additional diagnostic trouble codes, press the A/C button on the Manual A/C control. The BCM will beep each time the A/C button is pushed. Continue pushing the A/C button and recording the trouble code numbers until the odometer returns to normal operation (note the letters AC will disappear). It is important that no other knob or button is pushed until all codes are read. Pushing any button except the A/C button or turning a knob will end the diagnostic test without showing the rest of the trouble codes. There also may be other trouble codes stored in the BCM not related to the Climate Control System. These codes can only be found using the DRB scan tool.