Ignition Systems - Optical: Testing: Introduction
The ASD relay input continuously receives 12 volts from the battery. With ignition on, voltage is supplied to the ASD relay to activate the ASD relay pull-in coil, diagnostic connector and the SMEC terminal No. 58. The SMEC will then ground this terminal when it sees a toggling voltage from the distributor reference on circuit No. 12. The positive side of the coil is connected to battery positive when the ASD relay is grounded. See Fig 1.