Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provide an overview of each diagnostic category. |
DTC Descriptor
DTC P0401: Exhaust Gas Recirculation (EGR) Flow InsufficientDiagnostic Fault Information
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
EGR Valve DC Motor Control W, V and U | P0403, P0409 | P0403, P0409 | P0403, P0409 |
EGR Valve DC Motor Control W | P0403, P0409 | P0403, P0409 | P0403, P0409 |
EGR Valve DC Motor Control V | P0403, P0409 | P0403, P0409 | P0403, P0409 |
EGR Valve DC Motor Control U | P0403, P0409 | P0403, P0409 | P0403, P0409 |
EGR Position Sensor 5-Volt Reference | P0192, P02E8, P0409, P0462, P0642, P2453, P2454, P2564 | P0403, P0409 | -- |
EGR Throttle Position Sensor Signal W, V and U | P0403, P0409 | P0403, P0409 | P0403, P0409 |
EGR Throttle Position Sensor Signal W | P0403, P0409 | P0403, P0409 | P0403, P0409 |
EGR Throttle Position Sensor Signal V | P0403, P0409 | P0403, P0409 | P0403, P0409 |
EGR Throttle Position Sensor Signal U | P0403, P0409 | P0403, P0409 | P0403, P0409 |
EGR Throttle Position Sensor GND | -- | P0409 | -- |
Circuit/System Description
The engine control module (ECM) tests the exhaust gas recirculation (EGR) flow when the EGR is in operation. EGR desired flow is compared to EGR actual flow. If EGR flow is lower than expected DTC P0401 will set.
Conditions for Running the DTC
| • | DTCs P0027, P0079, P0080, P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0126, P0201, P0202, P0203, P0204, P0205, P0206, P0261, P0264, P0267, P0270, P0273, P0276, P02E7, P02E8, P0335, P0336, P0403, P0404, P0409, P0500, P0506, P0507, P0602, P0642, P0643, P0652, P0653, P1125, P1293, P2002, P2100, P2146, P2147, P2148, P2149, P2150, P2151, P2227, P2228, P2229, P2454, P2455, and P268A are not set. |
| • | The key switch is ON. |
| • | The power-up time is more than 5.056 seconds. |
| • | The battery voltage is between 10-16 volts. |
| • | The EGR valve test is complete. |
EGR Valve Test Mode Enable Conditions
| • | The engine speed is between 500-700 RPM. |
| • | The engine coolant temperature (ECT) is between 65-95°C (149-203°F). |
| • | The intake air temperature (IAT) is between -7 and +120°C (+19 and +248°F). |
| • | The barometric pressure (BARO) is more than 83 kPa. |
| • | The accelerator pedal position (APP) is less than 3 percent. |
| • | The vehicle speed is 3 km/h (2 mph). |
| • | The Ignition is ON. |
| • | The engine does NOT stall. |
| • | The EGR valve test is NOT complete. |
| • | The exhaust brake command is OFF. |
| • | The exhaust throttle command is OFF. |
| • | Intake throttle position is less than 60 percent. |
| • | The differential pressure is between -2 and +20 kPa. |
Conditions for Setting the DTC
The ECM detects that the mass air flow (MAF) amount is not within the calculated range for threshold during the EGR flow test for once per driving cycle.
Action Taken When the DTC Sets
DTC P0401 is a type B DTC.
Conditions for Clearing the DTC
DTC P0401 is a type B DTC.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Verification
- If DTC P0101, P0403, P0405, P0406, P0698, or P0699 are set diagnose these DTCs.
- Using the output controls on the scan tool command the EGR solenoid to 10 percent.
- Inspect the exhaust system for leaks, restrictions, or for modification of the original equipment manufacture (OEM) part.
- Visually inspect for leaks between the MAF sensor and the turbocharger.
- Visually inspect for a restriction in the air cleaner or the air intake ducts.
- Visually inspect for a restriction in the turbocharger charge air cooler.
- Visually inspect for a restriction in the intake manifold.
Important: If you cannot duplicate the condition, operate the vehicle within the conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
| ⇒ | If the actual EGR position remains stationary, replace the EGR valve. |
Circuit/System Testing
Inspect the charge air cooler for leaks.
| ⇒ | If no condition is found, perform the Component Testing. |
Component Testing
Important: Perform the Circuit/System Verification before proceeding with the Component Testing.
- Using the output controls on the scan tool command the EGR solenoid to 10 percent.
- Spray the EGR valve gaskets and EGR cooler gaskets with a soap solution. Start the engine. Command the turbocharger vane position control solenoid ON to 100 percent and inspect for leaks around the EGR valve gaskets.
- Inspect that the EGR is not stuck, that there are no leaks or restrictions in the EGR valve and EGR passages, and that there is no debris or damage that can cause the EGR valve to stick partially open or partially closed.
| ⇒ | If the actual EGR position remains stationary, replace the EGR valve. |
| ⇒ | If a leak is found, replace the EGR valve gasket. |
| ⇒ | If the EGR valve is sticking, or is damaged, replace the EGR valve. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
