LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Subaru >> 2018 >> WRX STI >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System (Diagnostics) (2 Of 4) (STI) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P0411: Secondary Air System Incorrect Flow Detected >> Notes
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0411: Secondary Air System Incorrect Flow Detected: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

CAUTION: After servicing or replacing faulty parts, perform Clear Memory Mode Ref. to ENGINE (DIAGNOSTICS) (STI)>Clear Memory Mode>OPERATION , and inspection mode Ref. to ENGINE (DIAGNOSTICS) (STI)>Inspection Mode>PROCEDURE .
  1. CHECK SECONDARY AIR COMBINATION VALVE  .

    Check the pipe between the secondary air combination valve and cylinder head.

    Is there damage or disconnection of the pipe?

    Yes:  Replace the pipe between secondary air combination valve and cylinder head. Ref. to EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES) (STI)>Secondary Air Combination Valve .

    No:  Go to  2

  2. CHECK SECONDARY AIR COMBINATION VALVE  .

    Race the engine at 2, 000 rpm to check whether or not the exhaust leak is heard.

    Is there any exhaust leak?

    Yes:  Replace the pipe between secondary air combination valve and cylinder head. Ref. to EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES) (STI)>Secondary Air Combination Valve .

    No:  Repair the poor contact of ECM connector.