Section 14 (Engine Controls - Tests W/Codes - 3.1L PFI): Introduction
WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 1990 Pontiac Grand Prix, 1990 Pontiac Firebird, 1990 Pontiac 6000, 1990 Oldsmobile Cutlass Supreme, and 1990 Chevrolet Lumina. However, it is still accessible from the selected car via links, so may be relevant.
Most engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged vacuum hoses. Before considering the computer system as a cause of problems, perform checks and inspections covered in BASIC TESTING article. Failure to do so may result in lost diagnostic time.
If no faults were found while performing the basic tests in the BASIC TESTING article, proceed with DIAGNOSTIC PROCEDURE in this article. If no fault codes or only a non-running Code 12 is present and driveability problems exist, proceed to article TESTS W/O CODES for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in the TESTS W/O CODES article in this section.