B1556 - BCM EPROM Write Error

Diagnostic Trouble Code Chart:

CIRCUIT DESCRIPTION
The module performs internal tests on the EPROM. Each time the module performs a write function to the EPROM, the module reads back the data that has been written and makes a comparison. If the data does not match after 3 consecutive write and verify attempts, the module will set B1556 as current.

CONDITIONS FOR SETTING THE DTC
^ The data read back after a write does not match the data being written after 3 consecutive attempts.
^ The condition must occur when data is being written.

ACTION TAKEN WHEN THE DTC SETS
^ A DTC B1556 is stored in the PZM memory.
^ No driver warning message is be displayed for this DTC.
^ The PZM stores the value being written in another memory address in the EPROM.

CONDITIONS FOR CLEARING THE DTC
^ This DTC requires a successful write in order to change from current to history.
^ The module no longer detects an internal write malfunction.
^ A history DTC clears after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.

DIAGNOSTIC AIDS
Since the EPROM cannot be removed from the module and DTC B1656 is an internal module malfunction, the module may need to be replaced.