P0491 on Volkswagen
Secondary Air Injection System Insufficient Flow (Bank 1)
P0491 on Volkswagen vehicles indicates secondary air injection system insufficient flow (bank 1). Au7o has documented this code across 1 Volkswagen model — most commonly on Jetta. This code means the PCM determined that the secondary air injection system is delivering insufficient airflow into the exhaust on Bank 1. This system pushes fresh air into the exhaust during cold starts to help the catalytic converter warm up quickly and lower emissions. Insufficient flow means the system isn't doing its job, usually due to a blockage, leak, or weak air pump. It typically triggers the check engine light and affects cold-start emissions rather than everyday driveability. Typical repair costs on Volkswagen range from $450 to $1,100, depending on the specific model and root cause.
Common Causes of P0491
- •Clogged or restricted secondary air injection passages
- •Failing secondary air injection pump
- •Stuck or leaking air switching/check valve
- •Vacuum or hose leak in the air injection plumbing
- •Carbon buildup blocking air delivery ports
- •Electrical fault in the pump or valve circuit
P0491 on Volkswagen by Model
Volkswagen Jetta(1 issue)
- Secondary Air Injection Pump and Combi Valve Failure (P0411) on the 2.5 Five-Cylinder2005-2014
The 2.5L five-cylinder Jetta (Mk5 2005-2010 and Mk6 2011-2014, engine codes BGP/BGQ/CBTA/CBUA) very commonly fails its secondary air injection system, which pumps air into the exhaust on cold start to light off the catalyst faster. The root cause is almost never the pump itself: the one-way combination valve (combi valve) between the pump and the exhaust fails and lets hot, moist exhaust gas back into the pump. That moisture corrodes the pump internals and, in winter, freezes - which is why many failures announce themselves on the first hard freeze, often blowing the pump fuse or burning out the J299 relay. The signature is a loud jet-engine or shop-vac roar for 60-90 seconds after a cold start, followed by a check engine light. The system only runs on cold start, so the car otherwise drives normally, but it is an emissions-test failure.
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What does P0491 mean on Volkswagen?▼
P0491 stands for "Secondary Air Injection System Insufficient Flow (Bank 1)." This code means the PCM determined that the secondary air injection system is delivering insufficient airflow into the exhaust on Bank 1. This system pushes fresh air into the exhaust during cold starts to help the catalytic converter warm up quickly and lower emissions. Insufficient flow means the system isn't doing its job, usually due to a blockage, leak, or weak air pump. It typically triggers the check engine light and affects cold-start emissions rather than everyday driveability. On Volkswagen specifically, this code is documented across 1 model.
What causes P0491 on Volkswagen vehicles?▼
Common causes on Volkswagen: Clogged or restricted secondary air injection passages, Failing secondary air injection pump, Stuck or leaking air switching/check valve, Vacuum or hose leak in the air injection plumbing, Carbon buildup blocking air delivery ports. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0491 on a Volkswagen?▼
Repair costs on Volkswagen range from $450 to $1,100, depending on the specific model and root cause.
Which Volkswagen models have P0491 documented?▼
Au7o has documented P0491 on 1 Volkswagen model: Jetta.