DTC P0401: EGR Abnormal (EGR Amount Too Small): Notes

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Trouble symptom:

Infrequent knocking (P0401)
Improper idling (P0402)
Movement performance problem (P0402)

NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

CHECK DTC .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
When a code other than DTC P0401 (current code) or P0402 (current code) is displayed, go to A.

When DTC P0401 (current code) is displayed, go to B.

When DTC P0402 (current code) is displayed, go to C.
1. Check the appropriate DTC using the "Diagnostic Trouble Code (DTC)". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .
2. Go to 2.
3. Go to 3.
CHECK DTC P0401 .
1. Turn the ignition switch to OFF.
2. Check for clogging in the pipes consisting of EGR system.
NOTE:
Check the following items.
- Throttle valve
- EGR cooler
- EGR control valve
- EGR pipe
- EGR pipe adapter
Is the check result OK?

Yes: Go to 4.

No: Clean and replace the faulty parts.
CHECK DTC P0402 .
1. Turn the ignition switch to OFF.
2. Check for leakage in the pipes consisting of the EGR system.
NOTE:
Check the following items.
- Looseness of each flange connection
- Improper installation of the electronic throttle control
- Improper installation of manifold absolute pressure and intake air temperature sensor
- Foreign matter attached to EGR valve
Is the check result OK?

Yes: Go to 4.

No: Clean and replace the faulty parts.
CHECK FOR REPRODUCTION OF FAILURE .
Perform the corresponding inspection mode. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>INSPECTION MODE .

Does the malfunction indicator light illuminate?

Yes: Replace the EGR control valve and manifold absolute pressure and intake air temperature sensor.

Ref. to EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES) (H4DOTC)>EGR CONTROL VALVE .

Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>MANIFOLD ABSOLUTE PRESSURE AND INTAKE AIR TEMPERATURE SENSOR .

No: End.