Cellular Communications System Diagnosis

DTC B1658 EEPROM Checksum Error:

CIRCUIT DESCRIPTION
The module calibrations are stored in the EEPROM. When the ignition is first turned ON, the module performs internal tests on the EEPROM and can determine the integrity of its non-volatile memory. The module compares its previously stored checksum with the checksum calculated when the ignition is first turned ON. If the two checksums do not match, the module will indicate a calibration malfunction (checksum error) is current.

CONDITIONS FOR SETTING DTC
^ The stored checksum does not match the calculated checksum.
^ The module detects an internal memory malfunction (checksum error).
^ The condition must occur when the ignition is first turned ON.

ACTION TAKEN WHEN THE DTC SETS
^ Stores a DTC B1658 in the module memory.
^ No driver warning message will be displayed for this DTC.
^ The module will use default values for any memory address in the EEPROM that is corrupt.

CONDITIONS FOR CLEARING DTC
^ This DTC requires an ignition cycle in order to change from current to history.
^ The module no longer detects an internal memory malfunction (checksum error).
^ A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ Use the On-Boards clearing DTCs feature.
^ Use a scan tool.

DIAGNOSTIC AIDS
Since the EEPROM cannot be removed from the module and DTC B1658 is an internal module malfunction, the module may need to be replaced. Refer to diagnostic table. Symptom Related Diagnostic Procedures

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table:
1. Perform the Diagnostic System Check before continuing with the diagnosis of this DTC.
2. Clear all DTCs and cycle ignition to check that the DTC did not falsely set.
4. Clear all DTCs after the repair procedure is complete.