B1658
CIRCUIT DESCRIPTIONThe EEPROM write error detection is handled inside the control module. No external circuits are involved. The module calibrations are stored in EEPROM (Electrically Erasable Programmable Rear Only Memory). When you turn ON the ignition, the module performs internal tests on the EEPROM. The test may determine the integrity of the nonvolatile memory. The module compares the previously stored checksum with a checksum calculated when the ignition turns ON. If the 2 checksums do not match, the module will indicate that a calibration malfunction (checksum error) is current.
CONDITIONS FOR SETTING THE DTC
^ The stored checksum does not match the calculated checksum.
^ The module detects an internal memory malfunction (checksum error).
^ The condition occurs when the ignition is first turned ON.
CONDITIONS FOR RUNNING THE DTC
The microprocessor runs the program to detect a write error whenever it writes to the EEPROM. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.
ACTION TAKEN WHEN THE DTC SETS
The microprocessor finds another area to write the information to. This new area becomes the permanent area for storage of this information.
CONDITIONS FOR CLEARING THE MIL/DTC
The DTC clears when the microprocessor makes a successful write to the EEPROM.
DIAGNOSTIC AIDS
^ This DTC may be stored as a history DTC with out affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
^ If this DTC is retrieved as both a current and history DTC, replace the module.
TEST
