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.
Circuit Description
The diagnostic system check - engine controls must be the starting point for any driveability complaint diagnosis. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. Perform a careful visual and physical inspection of the Powertrain Control Module (PCM) and engine grounds for being clean and tight. Diagnostic system check - engine controls is an organized approach to identifying a condition created by an electronic engine control system malfunction.
The Powertrain Control Module (PCM) controls the Malfunction Indicator Light (MIL) by providing a ground path through the MIL control circuit to turn ON the MIL. When the ignition is turned ON, the MIL will remain on until the engine is running, if no Diagnostic Trouble Codes (DTC) are stored. If MIL is illuminated, then engine stalls, the MIL will remain illuminated so long as ignition is ON.
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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.