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/System Description
The ignition relay is normally an open relay. The relay armature is held in the open position by spring tension. When the ignition switch is turned to the Run or Start position, current will flow through the relay coil. A wire connected to the other end of the relay coil completes the path to ground through the ECM. The electromagnetic field created by the relay coil overcomes the spring tension and moves the armature, allowing the contacts to close.
When the ignition switch is turned to the OFF position, the electromagnetic field collapses. This action allows the spring tension to move the armature away from the relay contacts, which interrupts current flow to the fuses.
If the ECM relay fails to close, the engine will not crank. Communication will not be available with the use of a scan tool.
The ECM relay table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test .
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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.