For 1990-2009 cars

### Circuit Description

The Integrated Radio Controller (IRC) keeps an EEPROM value that contains a checksum for each of its EEPROM blocks. These values are not included in the checksums of the blocks, but is a static, or read only value. The IRC computes a checksum for the EEPROM block and compares it to a checksum stored in the EEPROM. If the values do not match, then the IRC sets DTC B1658.

### Conditions for Setting the DTC

• | The stored checksum does not match the calculated checksum.

• | The IRC detects an intenal memory malfunction (checksum error).

• | The condition must occur when the ignition is first turned ON or within 2.5 seconds of the ignition being turned ON.

### Action Taken When the DTC Sets

• | DTC B1658 is stored in the IRC memory.

• | No driver warning message will be displayed for this DTC.

• | The IRC will use default values for any memory addres in the EEPROM that is corrupt.

### Conditions for Clearing the DTC

• | This DTC requires an ignition cycle in order to change from a current DTC to a history DTC.

• | The IRC 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.

### Diagnostic Aids

• | Since the EEPROM cannot be removed from the IRC and DTC B1658 is an internal IRC malfunction, the IRC needs to be replaced.

• | Replace the radio. Refer to Radio Replacement in Entertainment.