Circuit Description
The exhaust gas recirculation (EGR) solenoid and pintle valve assembly serve to reduce the temperature of combustion by introducing non-volatile exhaust gas into the combustion chambers. The EGR flow check diagnostic runs once per drive cycle after 1.5 kg of air has passed through the engine. The ECM compares the MAP sensor reading to a modeled value that it calculates. This code will set if the measured value is less than 70 percent of the modeled value.
DTC Parameters
DTC P0401 will set if the actual manifold pressure is less than 70 percent of the calculated pressure (based on engine load and EGR position) and:
| • | Engine speed is between 1600 and 2200 rpm |
| • | Engine load is between 35% and 60% |
| • | Altitude less than 9000 ft. |
P0401 is a (type B) DTC.
Diagnostic Aids
Carbon buildup around the EGR pintle valve bore opening may restrict exhaust gas flow, causing this DTC to set.
Diagnose other DTCs, especially a MAP DTC before diagnosing this code.
Possible Causes:
| • | EGR valve stuck closed or carbon plugged |
| • | EGR passage plugged restricting EGR flow |
| • | EGR |
