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.
How To Use Circuit Tests
1) DO NOT perform any CIRCUIT TEST unless directed to do so by a QUICK TEST procedure. Ensure all non-EEC related faults are corrected. FOLLOW EACH TEST STEP IN ORDER UNTIL FAULT IS FOUND. DO NOT replace any part unless directed to do so. When more than one service code is received, start with the first code displayed.
2) CIRCUIT TESTS require that you prove the electrical circuits are okay before you replace sensors or any other components. Always test circuits for continuity between the sensor and the ECA. Test all circuits for shorts to power, opens, or shorts to ground. Voltage Reference (VREF) and Voltage Power (VPWR) circuits should be tested with KOEO or as specified in the specific CIRCUIT TESTS (TESTS A1 to D3).
3) DO NOT measure voltage or resistance at ECA or connect any test light, unless specified in testing procedure. DO NOT pierce wiring. If backprobing is specified, always backprobe harness side of connector, never the connector side. Isolate both ends of a circuit and turn key off whenever checking for shorts or continuity, unless specified.
4) Unless otherwise specified, an open circuit is defined as a circuit which has a resistance greater than 5 ohms. Disconnect solenoids and switches before checking circuit continuity or energizing solenoids.
5) A short is defined as any resistance to ground of less than 10,000 ohms, unless otherwise specified.
Use the Manual With the Right Hardware
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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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