Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic System Check - Engine Controls
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.
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 .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.