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

Secondary air injection flow on bank 1 is lower than expected.

Code Overview

Secondary air injection flow on bank 1 is lower than expected.

Common Causes

• Failed secondary air pump or valve
• Restricted air passages or hoses
• Relay, fuse, or wiring issue

Diagnostic Steps

1. Inspect pump, valves, and hoses
2. Check fuse and relay operation
3. Command the system on if supported and confirm airflow

Likely Repairs & Cost Guides

Use test results to confirm the fault before pricing the repair.

Related OBD Codes

Browse the closest code-family pages when the same fault pattern often shows up nearby.

Next Steps

Move from the code to a diagnosis path, then into repair pricing once the fault is confirmed.