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.
EFI Main Relay
The EFI fuse supplies constant battery voltage to EFI main relay. When EFI main relay is energized by MRLY terminal of Engine Control Module (ECM), the EFI main relay provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. The EFI main relay also provides battery voltage to +B terminal of ECM when ignition is turned on.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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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