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Engaging The Pinion

Fig 1: Identifying Engine Control Module (ECM) And Starter Motor Relay
GLL154507Courtesy of VOLVO CARS CORPORATION

If the electronic immobilizer check is OK, the engine control module (ECM) (4/46) grounds and powers the starter motor relay (2/35). The relay is then activated and the control solenoid powered.

The control solenoid's position #2 (50) supplied with power from the relay. This creates a magnetic field in both pull-in and hold-in windings. This causes the moving steel core to shift. When the core shifts a lever, fixed in the end of the core, presses the starter motor pinion to engage in the ring gear on the flywheel/flange.

The pull-in winding is grounded through the rotor and carbon brushes. This ground connection is lost when the moving switches close the circuit and the current passes from the solenoid to the starter motor.