ISG System has alternator in which there is a communication regulator in order to compensate current loss resulting from repetitive starting. The alternator is duty controlled as current control by PCM with the battery voltage, current, temperature information from battery sensor. The more electrical load, the higher duty output.
PCM set DTC P0620 If it is open or short in Control circuit of alternator. If this DTC is set, Idle stop is not performing.
Item
Detecting Condition
Possible Cause
DTC Strategy
Signal check
Open or Short in harness
Poor connection or damaged harness
Enable Conditions
Desired alternator voltage duty cycle = 3.12%, = 94.5%
Engine speed >240rpm
Battery voltage <16V, >10.73V
Threshold Value
Open or Short circuit
Diagnostic Time
Continuous
MIL On Condition
DTC only(Idle stop forbidden)
Fig.1) Idle Status
Fig.2) Electrical Load (Head Lamp and Defrost are ON
Duty(+) from FR terminal is increased if electrical loads are ON (Head Lamp and Defrost are ON)
ECM controls generation of alternator with duty from FR terminal when electrical Loads turn on