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.
ECM Power Source Circuit: Description
When the power switch is turned on (IG), the battery voltage is applied to terminal IGSW of the hybrid vehicle control ECU. The hybrid vehicle control ECU MREL output signal causes a current to flow to the coil, closing the contacts of the IGCT relay and supplying power to terminal +B of the hybrid vehicle control ECU.
If the power switch is turned off, the hybrid vehicle control ECU holds the IGCT relay ON for a maximum of 2 seconds to allow for the initial setting of the throttle valve.
When the power switch is turned on (IG), voltage from the hybrid vehicle control ECU MREL terminal applies to the IGCT relay. This causes the contacts of the IGCT relay to close, which supplies power to terminal +B or +B1 of the hybrid vehicle control ECU.
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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.