P0491

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 most NAR (North American Market) 2009 to 2016 Audi models with 3.0L or 3.2L engines with P0491 and P0492 stored at same time, check to see if TPI 2033001 is applicable.
  • https://static.nhtsa.gov/odi/tsbs/2018/MC-10153120-9999.pdf NHTSA
    • 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

• When P0491 or P2440 are found in NAR (North American Market) 2013 to 2015 VW Jetta, Beetle and NMS Passat with 1.8T Engine codes CPPA, CPLA, CPKA and CPRA, check to see if TPI 2040822 / TSB 01-15-14 is applicable.
  • https://static.nhtsa.gov/odi/tsbs/2015/MC-10122989-9999.pdf NHTSA