P0491 - Secondary Air Injection (Air) System Insufficient Flow (Bank 1)

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P0491 - SECONDARY AIR INJECTION (AIR) SYSTEM INSUFFICIENT FLOW (BANK 1)

Description:	The secondary AIR system detected that there was insufficient mass air flow change during pump switching (ON/OFF).
Possible Causes:	Secondary AIR pump with no or low air flow Secondary AIR bypass solenoid leaking/blocked or stuck open/closed Secondary AIR diverter valve leaking/blocked or stuck open/closed Secondary AIR air hose restricted Secondary AIR vacuum hoes restricted or leaking
Diagnostic Aids:	Measured air flow is less than expected. Visually inspect the secondary AIR inlet hose.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
All	-	refer to PINPOINT TEST HM .	refer to PINPOINT TEST HM .