P0491

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P0491 - Secondary Air Injection System: Bank 1

P0491 - Secondary Air Injection System: Bank 1: Insufficient Flow

Possible Symptoms

  • Malfunction Indicator Light (MIL) active

Possible Causes

  • Fuse or relay for Secondary Air Injection Pump faulty
  • Hose(s)/Piping between Secondary Air Injection Pump and Combi (Secondary Air Injection) Valve leaking
  • Secondary Air Injection Solenoid(s) faulty
  • Secondary Air Injection Pressure Sensor faulty
  • Combi Valve(s) faulty
  • Secondary Air Injection ports in the cylinder head(s) plugged with carbon See Special Notes

Possible Solutions

  • Check fuse and relay for Secondary Air Injection Pump system.
  • Check hose(s)/Piping between Secondary Air Injection Pump and Combi Valve
  • Check Secondary Air Injection Solenoid(s)
  • Check Secondary Air Injection Pressure Sensor
  • Check Combi Valve(s)
  • Clean Secondary Air Injection ports in the cylinder head(s) if obstructed with carbon See Special Notes

Special Notes

  • When found in the following NAR (North American Market) Audi models listed below check to see if TPI 2033001 is applicable:
  • Audi TPI 2033001 pertains to P0491 and P0492 stored at same time on the following vehicles with more than 15,000 miles:
    • 2010+ S4 and S5 with CCBA 3.0L
    • 2008+ A5, 2009+ A4, 2011 A6 with CALA 3.2L
    • 2009-2011 A6 CCAA 3.0L
    • 2012 A6/A7 CGXB 3.0L
    • 2013+A6/A7 CTUA 3.0L
    • 2009+ Q5 CALB 3.2L
    • 2011+ Q7 CJWE, CJWC, CJWB 3.0L



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