Begin the system diagnosis by reviewing the Exterior Lighting Systems Description and Operation and the Interior Lighting Systems Description and Operation . Reviewing the Description and Operation information will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the Description and Operation information will also help you determine if the condition described by the customer is normal operation. Refer to Symptoms - Lighting Systems in order to identify the correct procedure for diagnosing the system and where the procedure is located.