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 Opening Relay
Circuit opening relay controls the fuel pump circuit. When EFI main relay is energized, EFI main relay provides battery voltage to circuit opening relay. When engine is cranking and start signal is delivered to Engine Control Module (ECM), the circuit opening relay ground circuit is grounded at ECM terminal FC. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. When start signal is released and engine is running, the ECM then uses engine speed input signal for controlling the ground circuit for circuit opening relay and provides voltage to fuel pump for fuel pump operation.
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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