Diagnostic Starting Point

ALLISON AUTOMATIC TRANSMISSION

Diagnostic Starting Point - Automatic Transmission
Begin the system diagnosis with Diagnostic System Check - Engine Controls in Engine Controls - 6.6L (LB7) or Diagnostic System Check - Engine Controls in Engine Controls - 8.1L. The Diagnostic System Check provides the following information:
^ The identification of the control modules which commands the system
^ The ability of the control modules 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 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 that no DTCs are present, begin symptom diagnosis by reviewing the Functional Test Procedure (Diagnostic Information and Procedures). 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 table. The Symptoms - Automatic Transmission table provides common diagnostic categories which relate directly to diagnostic information or procedures. Symptom Related Diagnostic Procedures