B1009 - HVAC Systems - Automatic
DTC B1009CIRCUIT DESCRIPTION
The EEPROM check sum error detection is handled inside the auxiliary HVAC control module.
CONDITIONS FOR RUNNING THE DTC
The microprocessor runs the program to detect a check sum error after each "power up". The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.
CONDITIONS FOR SETTING THE DTC
The microprocessor retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The microprocessor then reads the information from those certain blocks and adds the stored inverse value to the current value. If they do not equal 0, the microprocessor sets this DTC.
ACTION TAKEN WHEN THE DTC SETS
The microprocessor reverts to base operation values programed for those blocks of data that have failed the check sum test. The blocks of data that have not failed the check sum test are not affected.
CONDITIONS FOR CLEARING THE MIL/DTC
The DTC clears when the microprocessor runs a successful check sum test of the EEPROM.
DIAGNOSTIC AIDS
- Disconnecting and reconnecting the auxiliary HVAC control module connector with the ignition ON will set this DTC.
- An intermittent loss of battery positive voltage or ground may set this DTC.
TEST
