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 (DIAG)>DIAGNOSTIC TROUBLE CODE (DTC) .
Are DTCs P0401 and P0402 displayed? (Current malfunction)

Yes:
- DTC P0401 displayed: Go to 2.
- DTC P0402 displayed: Go to 3.
No: Check the appropriate DTC using the "Diagnostic Trouble Code (DTC)". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .
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 throttle body
  - 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>REMOVAL . Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>MANIFOLD ABSOLUTE PRESSURE AND INTAKE AIR TEMPERATURE SENSOR>REMOVAL .

No: End.