B1658 Pass-Key (R) III Module Checksum Error

CIRCUIT DESCRIPTION
The EEPROM Checksum diagnostic runs only at power-up. A checksum is calculated for each write data block as it is written and then stored at the end of that data block. During power-up the checksum for each data block is recalculated and compared with the stored checksum. Any mismatch between checksums will set this Diagnostic Trouble Codes (DTC).

CONDITIONS FOR SETTING THE DTC
This diagnostic runs at power up.

ACTION TAKEN WHEN THE DTC SETS
EEPROM Ignition Cycle Counter Data Blocks will be set to factory default.

CONDITIONS FOR CLEARING THE MIL/DTC
This DTC will be automatically cleared when the module calculates a successful EEPROM checksum.

TEST DESCRIPTION
The PASS-Key (R) III Module contains software programs that perform periodic self tests. The entire diagnostic function is done within the PASS-Key (R) III Module. Diagnostic results are reported over the Class 2 Data Link upon request from a Scan Tool.