Ignition Switch Controlled

This EFI Main Relay circuit is one of the most popular power distribution schemes used on late model TCCS equipped engines. It is used on most applications without a stepper type Idle Speed Control Valve (ISCV).

When the ignition switch is turned to the "run" or "start" position, current is supplied to the pull-in winding of the relay. Pull-in ground is wired directly to the vehicle chassis. ECU BATT voltage is supplied from the STOP fuse on these applications.

When the ignition switch is turned to the "run" or "start" position, current is supplied to the pull-in winding of the relay. Pull-in ground is wired directly to the vehicle chassis. The only power feed to the ECU on this system is the +B circuit.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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