Diagnostic System Check - Engine Controls

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The Diagnostic System Check - Engine Controls is an organized approach to identify a problem caused by an electronic engine control system malfunction. This diagnostic check must be the starting point for any driveability complaint diagnosis. The diagnostic directs the technician to the next logical step in diagnosing the complaint.

Use the Engine Scan Tool Data Definitions list for a comparison after fulfilling the following items:

Complete the Diagnostic System Check-Engine Controls.
Confirm that the on-board diagnostics are functioning properly.
Confirm there are no diagnostic trouble codes.

The Engine Scan Tool Definitions are an average of display values recorded from normal operating vehicles. The definitions intend to represent what a normal functioning system should display.

IMPORTANT: Do not use a scan tool that displays faulty data. Report the problem to the manufacturer. Using a malfunctioning scan tool can result in misdiagnosis and unnecessary parts replacement.

Use only the parameters listed in the Engine Scan Tool Data Definitions for diagnosis. When a scan tool reads other parameters, General Motors recommends not using the values for use in diagnosis.

For more description on the values and the use of the scan tool to diagnose the ECM inputs, refer to the applicable diagnostic file.

When all the values are within the range illustrated in the Engine Scan Tool Data Definitions, refer to Symptoms - Engine Controls .