Signal Wave Form & Data

This signal wave forms shows how MAIN RELAY and FUEL PUMP operate each other.

Fig 1: Main Relay And Fuel Pump Operation Signal WAVE FORMS

Courtesy of HYUNDAI MOTOR CO.

1. Point (1) is the duration PCM makes FUEL PUMP RELAY ON for 1.5 second after ignition switch ON.
2. Point (2) is MAIN RELAY ON and its voltage should be over 12V.
3. Point (3) is where PCM makes FUEL PUMP ON when it detects starting RPM (50) with CKPS signal.