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.
Engine Controls - System/Component Tests: Introduction
Before testing separate components or systems, perform all procedures listed in BASIC TESTING article in the ENGINE PERFORMANCE Section. Since many computer-controlled and monitored components will set a trouble code if they malfunction, it is also recommended that self-diagnosis be performed. See appropriate G - TESTS W/ CODES article in the ENGINE PERFORMANCE Section.
IMPORTANT: The following table provides the location of commonly used diagnostic information. These former "A" and "C" charts are now written in text and inserted into the appropriate location in the new Engine Performance workflow. To familiarize yourself with the Engine Performance workflow, see AA - USING THIS SECTION in the ENGINE PERFORMANCE Section
| System Or Component | Diagnostic Information Location | ||
|---|---|---|---|
| A-1 & A-2, SERVICE ENGINE SOON Light | See DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING | ||
| A-3, No Start | See NO START - ENGINE CRANKS OKAY in BASIC TESTING | ||
| A-5, Fuel Pump Relay | See FUEL SYSTEM in I - SYS/COMP TESTS | ||
| A-7, Fuel System Diagnosis | See BASIC FUEL SYSTEM CHECKS in BASIC TESTING | ||
| C-1, MAP Sensor | See ENGINE SENSORS & SWITCHES in I - SYS/COMP TESTS | ||
| C-1, Power Steering Pressure Switch | See ENGINE SENSORS & SWITCHES in I - SYS/COMP TESTS | ||
| C-1, Park/Neutral Switch | See ENGINE SENSORS & SWITCHES in I - SYS COMP TESTS | ||
| C-2, Injector Balance Test | See FUEL SYSTEM in I - SYS COMP TESTS | ||
| C-2, IAC Motor | See IDLE CONTROL SYSTEM in I - SYS COMP TESTS | ||
| C-2, ISC Motor | See IDLE CONTROL SYSTEM in I - SYS COMP TESTS | ||
| C-3, Canister Purge System (Fuel Evaporation Control) | See EMISSIONSYSTEMS & SUB-SYSTEMS in I - SYS COMP TESTS | ||
| C-4, EST Ignition Check | See BASIC IGNITION SYSTEM CHECKS in BASIC TESTING | ||
| C-5, ESC Ignition Check | See IGNITION SYSTEM in I - SYS COMP TESTS | ||
| C-6, Air Injection System | See EMISSION SYSTEMS & SUB-SYSTEMS in I - SYS COMP TESTS | ||
| C-7, EGR System | See EMISSION SYSTEMS & SUB-SYSTEMS in I - SYS COMP TESTS | ||
| C-8, Torque Converter Clutch (Transmission) | (1) See MISCELLANEOUS ECM CONTROLS in I - SYS COMP TESTS | ||
| C-8, Manual Transmission Shift Lights (Transmission) | (1) See MISCELLANEOUS ECM CONTROLS in I - SYS COMP TESTS | ||
| C-10, A/C Clutch Control | See MISCELLANEOUS ECM CONTROLS in I - SYS COMP TESTS | ||
| C-12, Electric Cooling Fan Control | See MISCELLANEOUS ECM CONTROLS in I - SYS COMP TESTS | ||
| C-18, Supercharger Boost Control | See AIR INDUCTION SYSTEMS in I - SYS COMP TESTS | ||
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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.
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