For 1990-2009 cars

### Circuit Description

The calibrations for the heater and A/C control are stored in EEPROM. When the ignition is first turned On, the controller performs internal tests on the EEPROM to determine if the EEPROM is programmed.

### Conditions for Setting the DTC

• | The test byte in EEPROM has an incorrect value (EEPROM not programmed.)

• | This fault is immediately recognized when the ignition is first turned On.

### Action Taken When the DTC Sets

• | Stores a DTC 52 in the controllers memory.

• | The heater and A/C control uses default values.

### Conditions for Clearing the DTC

• | Programming the heater and A/C control.

• | The use of a scan tool.

• | A history DTC will clear after 20 consecutive ignition cycles if the condition for the fault is no longer present.

### Diagnostic Aids

• | Install the scan tool

• | Select PROGRAMMING from the HEATER and A/C CONTROL main menu.

• | Program the heater and A/C control. Follow the instructions on the display screen.

• | If the heater and A/C control can not be programmed with the scan tool, check all power and ground circuits to the controller. If OK, replace the controller. Refer to Control Assembly Replacement .