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NOTE: This article applies for vehicles/models that were not equipped with On Board Diagnostics II (OBD II) system.

Most engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged vacuum hoses. Before considering the computer system as a possible cause of problems, perform checks and inspections covered in appropriate BASIC TESTING article in this section. Failure to do so may result in lost diagnostic time.

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed with DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no fault codes are present and driveability problems exist, proceed to TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in TESTS W/O CODES article in this section.