Code result
P0491
Secondary Air Injection System Insufficient Flow
Moderate severity
What it means
AIR system flow on bank 1 is below threshold during the cold-start self-test — typically a clogged check valve, leaking hose, or weak air pump.
Is it safe to drive?
Use caution
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Check valve clogged with carbon
highOne of the most commonly reported causes for this code — check this first.
Air pump weak
mediumA plausible cause — test and verify before replacing parts.
Related help
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