GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The radio (IRC) calibrations are stored in EEPROM (Electronically Erasable Programmable Read Only Memory).

The radio (IRC) performs internal tests on the EEPROM. The radio attempts to write to its EEPROM and then reads the data back. This test determines the integrity of the non-volatile memory.

Conditions for Setting the DTC

When the ignition is turned ON, the radio (IRC) performs internal tests on the EEPROM. The test determines the integrity of the non-volatile memory. If the data read by the radio (IRC) does not match the data written to the EEPROM after two consecutive attempts, the radio will set DTC B1656 as current.

Action Taken When the DTC Sets

    • DTC B1656 is stored in the module.
    • This DTC does not cause driver warning message to be displayed.

Conditions for Clearing the DTC

    • The data read by the radio (IRC) matches the data written to the EEPROM.
    • A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids

If DTC B1656 is set, clear the DTCs and cycle the ignition. If DTC B1656 is still current, replace the radio (IRC). Refer to one of the flowing:

    •  Radio Replacement
    •  Radio Replacement