The starter control system prevents the starter from accidentally activating when the shift position is not in P or N position/mode (CVT) or the clutch pedal is released (M/T), or when the engine is running. If the vehicle is turned mistakenly while shift position is not in P or N position/mode (CVT) or the clutch pedal is released (M/T) or while the engine is running, the powertrain control module (PCM) will stop power to the starter cut relay circuits. However, cranking to return from auto idle stop does not correspond to this (if equipped). In this system, two starter cut relay circuits are connected in series (starter cut relay 1 circuit, starter cut relay 2 circuit) to prevent the starter from running continuously due to a starter cut relay circuit malfunction. Also a diagnosis line (ST RLY 1 TO 2) is connected to monitor the voltage between the starter cut relay 1 circuit and starter cut relay 2 circuit. Based on the diagnosis line signals, the PCM detects an OPEN malfunction of diagnosis line, an ON malfunction of starter cut relay 1 circuit, and an ON malfunction of starter cut relay 2 circuit. The PCM also equips with return signal circuits of starter cut relay 1 circuit and starter cut relay 2 circuit to detect an OFF malfunction. If the voltage of the diagnosis line (ST RLY 1 TO 2) input does not exceed the upper and lower limits for a specified duration when the starter is ON (STS ON), the PCM detects an OPEN malfunction of the diagnosis line and stores a DTC.