Begin the diagnosis of the Data Link Communications System by performing the Diagnostic System Check for the system in which the customer concern is apparent. The correct procedure can be located by referring to Control Module References . The Diagnostic System Check will direct you to the correct procedure within the Data Link Communications section when a communication malfunction is present.

If Class 2 communication malfunction is a symptom, check SP261 (splice pack 261) to verify a tight connection between the connector and the bus bar that clips on to the assembly. Refer to one of the symptoms below to diagnose a Data Link malfunction:

Also refer to Data Link Communications Circuit Description for a functional description of the Data Link system.