Ignition Coil & Power Transistor

The ignition signal from the ECM is sent to and amplified by the power transistor. The power transistor turns ON and OFF the ignition coil primary circuit. This ON-OFF operation induces the proper high voltage in the coil secondary circuit.

Fig 1: Identifying Ignition Coil With Power Transistor

Courtesy of NISSAN MOTOR CO., U.S.A.