After taking my car to the drag strip one night I've got this PO401 code [ EGR valve insufficient ]. I cleared the code, but light came back on. I was hoping someone else may have seen this after running one hard, and would know what to look at first. 2014 GT500 with 4700 mi, I haven't noticed any driving issue.
PO401 Code
- Thread starter Dragfan
- Start date
P0401 - Exhaust Gas Recirculation (EGR) Flow Insufficient Detected
| Description: | The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the differential pressure feedback EGR sensor indicates that EGR flow is less than the desired minimum. |
| Possible Causes: |
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| Diagnostic Aids: | Carry out the key ON, engine running (KOER) self-test and look for DTC P1408 as an indication of a hard fault. If DTC P1408 is not present, look for contamination, restrictions, leaks, and intermittent concerns. |
Exhaust Gas Recirculation (EGR) Systems
OverviewThe EGR system controls the nitrogen oxides (NOx) emissions. Small amounts of exhaust gases are recirculated back into the combustion chamber to mix with the air to fuel charge. The combustion chamber temperature is reduced, lowering NOx emissions.
Electric Exhaust Gas Recirculation (EEGR) System
Highlights Of The EEGR System
- The EEGR valve is activated by an electric stepper motor.
- Engine coolant is routed through the assembly on some vehicle applications. Some vehicle applications are air cooled.
The EEGR system uses exhaust gas recirculation to control the NOx emissions just like vacuum operated systems. The only difference is the way in which the exhaust gas is controlled.
The EEGR system consists of an electric motor EGR valve integrated assembly, a PCM, and connecting wiring. Additionally a manifold absolute pressure (MAP) sensor is also required. For additional information on the EGR system components, refer to Engine Control Components in this section. Operation of the system is as follows:
- The EEGR system receives signals from the engine coolant temperature (ECT) or cylinder head temperature (CHT) sensor, throttle position (TP) sensor, mass airflow (MAF) sensor, crankshaft position (CKP) sensor, and the MAP sensor to provide information on engine operating conditions to the PCM. The engine must be warm, stable, and running at a moderate load and RPM before the EEGR system is activated. The PCM deactivates the EEGR during idle, extended wide open throttle (WOT), or whenever a concern is detected in an EEGR component or EGR required input.
- The PCM calculates the desired amount of EGR for a given set of engine operating conditions.
- The PCM in turn outputs signals to control the EEGR motor to move (advance or retract) a calibrated number of discrete steps. The electric stepper motor directly actuates the EEGR valve, independent of engine vacuum. The EEGR valve is commanded from 0 to 52 discrete steps to get the EGR valve from a fully closed to a fully open position. The position of the EGR valve determines the EGR flow.
- A MAP sensor measures variations in manifold pressure as exhaust gas recirculation is introduced into the intake manifold. Variations in EGR being used correlate to the MAP signal (increasing EGR increases manifold pressure values).
EEGR System
Overview
The ESM functions in the same manner as a conventional differential pressure feedback EGR system, however the various system components have been integrated into a single component called the ESM. For additional information on the ESM system components, refer to Engine Control Components in this section. The flange of the valve portion of the ESM bolts directly to the intake manifold. This arrangement increases system reliability, response time, and system precision. By relocating the EGR orifice from the exhaust to the intake side of the EGR valve, the downstream pressure signal measures manifold absolute pressure. This manifold absolute pressure signal is used for EGR correction and inferred barometric pressure (BARO) at ignition ON. The system provides the PCM with a differential pressure feedback EGR signal.
First, the differential pressure feedback EGR sensor input circuit is checked for out of range values (DTC P0405 or P0406). The EGR vacuum regulator output circuit is checked for opens and shorts (DTC P0403).
The EGR system normally has large amounts of water vapor that are the result of the engine combustion process. During cold ambient temperatures, under some circumstances, water vapor can freeze in the differential pressure feedback EGR sensor, hoses, as well as other components in the EGR system. To prevent malfunction indicator lamp (MIL) illumination for temporary freezing, the following logic is used.
If an EGR system concern is detected below 0°C (32°F), only the EGR system is disabled for the current driving cycle. A DTC is not stored and the inspection/maintenance (I/M) readiness status for the EGR monitor does not change. The EGR monitor, however, continues to operate. If the EGR monitor determines the concern is no longer present, the EGR system is enabled and normal system operation is restored.
If an EGR system concern is detected above 0°C (32°F), the EGR system and the EGR monitor are disabled for the current driving cycle. A DTC is stored and the MIL is illuminated if the concern has been detected for 2 consecutive driving cycles.
After the vehicle has warmed up and normal EGR rates are being commanded by the PCM, the low flow check is carried out. Since the EGR system is a closed loop system, the EGR system delivers the requested EGR flow as long as it has the capability to do so. If the EGR vacuum regulator duty cycle is at maximum (90% duty cycle), the differential pressure indicated by the differential pressure feedback EGR sensor is evaluated to determine the amount of EGR system restriction. If the differential pressure is below a calibrated threshold, a low flow concern is indicated (DTC P0401 or P0406).
Finally, the differential pressure indicated by the differential pressure feedback EGR sensor is also checked at idle with zero requested EGR flow to carry out the high flow check. If the differential pressure exceeds a calibrated limit, it indicates a stuck open EGR valve or debris temporarily lodged under the EGR valve seat (DTC P0402).
If the inferred ambient temperature is less than 0°C (32°F), or greater than 60°C (140°F), or the altitude is greater than 8,000 feet (BARO less than 22.5 in-Hg), the EGR monitor cannot be run reliably. A timer starts to accumulate the time in these conditions. If the vehicle leaves these extreme conditions, the timer starts to decrement and, if conditions permit, attempts to complete the EGR flow monitor. If the timer reaches 800 seconds, the EGR monitor is disabled for the remainder of the current driving cycle and the EGR monitor I/M readiness bit is set to a ready condition after one such driving cycle. Vehicles require 2 such driving cycles for the EGR monitor to be set to a ready condition.
Last edited:
Thanks for the info. When I get some time I'll see what I can find in the next few days.Exhaust Gas Recirculation (EGR) Systems
Overview
The EGR system controls the nitrogen oxides (NOx) emissions. Small amounts of exhaust gases are recirculated back into the combustion chamber to mix with the air to fuel charge. The combustion chamber temperature is reduced, lowering NOx emissions.
Electric Exhaust Gas Recirculation (EEGR) System
Highlights Of The EEGR System
Overview
- The EEGR valve is activated by an electric stepper motor.
- Engine coolant is routed through the assembly on some vehicle applications. Some vehicle applications are air cooled.
The EEGR system uses exhaust gas recirculation to control the NOx emissions just like vacuum operated systems. The only difference is the way in which the exhaust gas is controlled.
The EEGR system consists of an electric motor EGR valve integrated assembly, a PCM, and connecting wiring. Additionally a manifold absolute pressure (MAP) sensor is also required. For additional information on the EGR system components, refer to Engine Control Components in this section. Operation of the system is as follows:
Exhaust Gas Recirculation (EGR) System Module (ESM)
- The EEGR system receives signals from the engine coolant temperature (ECT) or cylinder head temperature (CHT) sensor, throttle position (TP) sensor, mass airflow (MAF) sensor, crankshaft position (CKP) sensor, and the MAP sensor to provide information on engine operating conditions to the PCM. The engine must be warm, stable, and running at a moderate load and RPM before the EEGR system is activated. The PCM deactivates the EEGR during idle, extended wide open throttle (WOT), or whenever a concern is detected in an EEGR component or EGR required input.
- The PCM calculates the desired amount of EGR for a given set of engine operating conditions.
- The PCM in turn outputs signals to control the EEGR motor to move (advance or retract) a calibrated number of discrete steps. The electric stepper motor directly actuates the EEGR valve, independent of engine vacuum. The EEGR valve is commanded from 0 to 52 discrete steps to get the EGR valve from a fully closed to a fully open position. The position of the EGR valve determines the EGR flow.
- A MAP sensor measures variations in manifold pressure as exhaust gas recirculation is introduced into the intake manifold. Variations in EGR being used correlate to the MAP signal (increasing EGR increases manifold pressure values).
EEGR System
Overview
The ESM functions in the same manner as a conventional differential pressure feedback EGR system, however the various system components have been integrated into a single component called the ESM. For additional information on the ESM system components, refer to Engine Control Components in this section. The flange of the valve portion of the ESM bolts directly to the intake manifold. This arrangement increases system reliability, response time, and system precision. By relocating the EGR orifice from the exhaust to the intake side of the EGR valve, the downstream pressure signal measures manifold absolute pressure. This manifold absolute pressure signal is used for EGR correction and inferred barometric pressure (BARO) at ignition ON. The system provides the PCM with a differential pressure feedback EGR signal.
First, the differential pressure feedback EGR sensor input circuit is checked for out of range values (DTC P0405 or P0406). The EGR vacuum regulator output circuit is checked for opens and shorts (DTC P0403).
The EGR system normally has large amounts of water vapor that are the result of the engine combustion process. During cold ambient temperatures, under some circumstances, water vapor can freeze in the differential pressure feedback EGR sensor, hoses, as well as other components in the EGR system. To prevent malfunction indicator lamp (MIL) illumination for temporary freezing, the following logic is used.
If an EGR system concern is detected below 0°C (32°F), only the EGR system is disabled for the current driving cycle. A DTC is not stored and the inspection/maintenance (I/M) readiness status for the EGR monitor does not change. The EGR monitor, however, continues to operate. If the EGR monitor determines the concern is no longer present, the EGR system is enabled and normal system operation is restored.
If an EGR system concern is detected above 0°C (32°F), the EGR system and the EGR monitor are disabled for the current driving cycle. A DTC is stored and the MIL is illuminated if the concern has been detected for 2 consecutive driving cycles.
After the vehicle has warmed up and normal EGR rates are being commanded by the PCM, the low flow check is carried out. Since the EGR system is a closed loop system, the EGR system delivers the requested EGR flow as long as it has the capability to do so. If the EGR vacuum regulator duty cycle is at maximum (90% duty cycle), the differential pressure indicated by the differential pressure feedback EGR sensor is evaluated to determine the amount of EGR system restriction. If the differential pressure is below a calibrated threshold, a low flow concern is indicated (DTC P0401 or P0406).
Finally, the differential pressure indicated by the differential pressure feedback EGR sensor is also checked at idle with zero requested EGR flow to carry out the high flow check. If the differential pressure exceeds a calibrated limit, it indicates a stuck open EGR valve or debris temporarily lodged under the EGR valve seat (DTC P0402).
If the inferred ambient temperature is less than 0°C (32°F), or greater than 60°C (140°F), or the altitude is greater than 8,000 feet (BARO less than 22.5 in-Hg), the EGR monitor cannot be run reliably. A timer starts to accumulate the time in these conditions. If the vehicle leaves these extreme conditions, the timer starts to decrement and, if conditions permit, attempts to complete the EGR flow monitor. If the timer reaches 800 seconds, the EGR monitor is disabled for the remainder of the current driving cycle and the EGR monitor I/M readiness bit is set to a ready condition after one such driving cycle. Vehicles require 2 such driving cycles for the EGR monitor to be set to a ready condition.
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