GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The radio (IRC) performs internal tests on the EEPROM each time that the radio performs a write function to a memory address in the EEPROM. The radio reads back the data that has been written and compares it to the data it wrote.

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

    • The radio stores a DTC B1656 in its memory.
    • No driver warning message is displayed for this DTC.
    • The radio stores the value being written in another memory address in the EEPROM.

Conditions for Clearing the DTC

    • This DTC requires a successful write in order to change from current to history.
    • A history DTC clears after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids

Since the EEPROM cannot be removed from the radio, DTC B1656 is an internal radio malfunction, the radio may need to be replaced.

Test Description

The numbers below refer to the step numbers on the diagnostic table:

  1. Perform the Radio/Audio System 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.

  3. Clear all DTCs after the repair procedure is complete.

Step

Action

Value(s)

Yes

No

1

Was the Radio/Audio System Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Radio/Audio System

2

  1. Turn the ignition switch to ON.
  2. Clear any DTCs.
  3. Turn the ignition switch to OFF.
  4. Turn the ignition switch to ON.

Is the DTC still present?

--

Go to Step 3

Go to Diagnostic System Check - Radio/Audio System

3

Replace the radio. Refer to Radio Replacement .

Is the repair complete?

--

Go to Step 4

--

4

  1. Turn the ignition switch to OFF.
  2. Reconnect or install any connectors or components that were disconnected or removed.
  3. Turn the ignition switch to ON.
  4. Clear any DTCs.

Are all DTCs cleared?

--

Go to Diagnostic System Check - Radio/Audio System

--