P0490 Buick Exhaust Gas Recirculation Throttle Control Circuit A Circuit High

P0491 Buick Secondary Air Injection System Insufficient Flow Bank 1

Possible causes
– Secondary air pump with no or low air flow
– Secondary air bypass solenoid leaking /blocked or stuck open /closed
– Secondary AIR air hose restricted
– Secondary air vacuum hoses restricted or leaking
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
P0491 Buick Description

The secondary air system detected that there was insufficient mass flow change during pump switching (on/off)

Buick Vehicle:Buick Regal – ?Buick Riviera – ?Buick LaCrosse – ?David Dunbar Buick – Buick Century – Buick LaCrosse – Buick LeSabre – Buick Lucerne – Buick Park Avenue – Buick Regal – Buick Verano – Buick Enclave – Buick Encore – Buick Rainier – Buick Rendezvous – Buick Terraza – Buick Riviera