Diagnostic Starting Point

ALLISON AUTOMATIC TRANSMISSION

Diagnostic Starting Point - Automatic Transmission
Begin the system diagnosis with Diagnostic System Check - Engine Controls in Engine Controls-6.6 L or Diagnostic System Check - Engine Controls in Engine Controls-8.1 L. The Powertrain OBD System Check provides the following information:
^ The identification of the control module which commands the system.
^ The ability of the control module(s) to communicate through the serial data circuit.
^ The identification and status of stored Diagnostic Trouble Codes (DTCs).

The use of Diagnostic System Check - Engine Controls in Engine Controls-6.6 L or Diagnostic System Check- Engine Controls in Engine Controls-8.1 L identifies the correct procedure for diagnosing the system and where the procedure is located.

Symptoms
When it has been determined through Diagnostic System Check - Engine Controls in Engine Controls-6.6 L or Diagnostic System Check - Engine Controls in Engine Controls-8.1 L that no DTCs are present, begin symptom diagnosis by reviewing the Functional Test Procedure. This helps you determine if the condition described by the customer is normal or if a malfunction exists. If it is determined that a malfunction exists, identify the concern by referring to the Symptoms - Automatic Transmission. The Symptoms - Automatic Transmission table provides common diagnostic categories which relate directly to diagnostic information or procedures.