OBD-II Generic Error Code P0491: How to Fix It

Q: What does secondary air injection insufficient flow mean?

It means the pump that pushes fresh air into the exhaust is not delivering enough air, usually due to a failed pump, blocked hoses, or defective check valve.

Q: Can I drive with a P0491 code?

Yes, you can usually drive, but the check engine light will stay on. The car may fail an emissions test. Continued driving with a faulty pump can cause other issues, so it's best to fix it soon.

Q: How much does it cost to fix P0491?

DIY costs range from $20 for a new relay to $200 for an air pump. Professional repair can be $300-$600 including labor.

Q: Is error code P0491 serious?

It is moderately serious. While the car is still drivable, the emissions system is compromised and could lead to a failed inspection or damage to the catalytic converter over time.

Q: What parts are needed to fix P0491?

Common parts include a secondary air injection pump, check valve, relay, and hoses. The exact part depends on your vehicle make and model.

Abstract

Error code P0491 indicates that the secondary air injection system on bank 1 is not providing enough airflow. This system pumps fresh air into the exhaust to reduce emissions during cold starts. A faulty pump, clogged hoses, or a blown fuse can cause this code. Here's how to diagnose and fix it.