The voltage after the main relay is used to supply power to the sensors and actuators.
ECM controls the main relay and its remains ON at key OFF in order to store the adaptaion values and fault status to the memory.
When the ignition switch is turned ON, current flows from the ignition switch through the current and the main relay coil to ground by the ECM.
And then, the voltage is supplied to the sensors and actuators to drive.
In case of the the main relay failure, the engine symptoms will occur a running engine stall, a starting impossible and glow plug deactivation.
If the signal exceeds threshold value, the ECM judged this as a fault and DTC is set.
Item
Detecting Condition
Possible Cause
DTC Strategy
? Circuit continuity check
? Opne or short in power circuit
? Open or short in relay control circuit
? Faulty relay
? Faulty ECM
Enable Conditions
? Ignition on and off
Threshold Value
? main relay shut off time is too early or late when comeparing the ignition on/off time with the ECM microcomputer signal.
Diagnostic Time
? 0 sec.
MIL
Fuel Limit
Fuel Cut
EGR Off
? Yes
? No
Fail safe
? EGR valve deactivited
? Fuel quantity limitation