Receiving ECM signal, linear solenoid type electronic EGR actuator operates Electric EGR control valve directly.
ECM performs EGR system feed back control with the information of measured mass air flow (The role of MAFS in diesel engine is different from gasoline engine. Fuel injection quantity is decided by MAFS signal in gasoline engine.)
When EGR gas(contains no oxygen) flowing into combustion chamber increases, the air passing through AFS(contains oxygen) decreases. Thus, with the output signal change of AFS accompanied by Electric EGR control valve actuation, ECM determine the amount of recirculated EGR gas quantity.
NOx is produced from the reaction of nitrogen and oxygen.
Controlling EGR gas(contains no oxygen) which is recirculated to combustion chamber, if least intake air required for complete combustion flows into combustion chamber, NOx decreases because there is no supplementary oxygen to react with nitrogen.
P401 is set when ECM detects that duty amount of EEGR actuator contol valve, ENG speed or amount of EGR is exceeded to minimum set point last to more than 15sec. In this case, check that stuck of EEGR actuator, air leakage of intake line.
Item
Detecting Condition
Possible Cause
DTC Strategy
Signal monitoring
EGR actuator stuck
EGR actuator component
Air leakage of intake line
Enable Conditions
Engine running
Threshold Value
Real value - Target value > upper specified air amout value
Diagnostic Time
15 sec.
Fail Safe
Fuel cut
NO
EGR Off
YES
Fuel Limit
MIL
Electric EGR control valve
component resistance
operating Hz
operating duty
EGR Position Sensor
7.5~8.5O (20?)
142Hz
5%(closed)~39±10%(opened)
4KO±40%
Fig.1) Approx. 5% duty signal waveform of Electric EGR control valve (with EEGR valve closed)
Fig.2) Approx. 57% duty signal waveform of Electric EGR control valve(with EEGR valve opened)
The output of approx. 5% duty is mainly for the diagnosis of Electric EGR control valve circuit than actuating EEGR.