EGR valve

P0491 Secondary air system: flow too low (bank 1)

By: Diagno editorial team · Updated: 2026-10-15

P0491 means: Secondary air system: flow too low (bank 1). The secondary air system blows air into the exhaust on a cold start so the catalytic converter warms up faster. OK to drive, but have it checked soon. The repair usually costs about €80–600 in Estonia.

Is it safe to drive?OK to driveOK to drive, but have it checked soon.

Typical repair cost€80–600parts and labour in Estonia

What it means

The secondary air system blows air into the exhaust on a cold start so the catalytic converter warms up faster. The computer found too little air or a fault in the pump or valve control.

What you may notice

Engine light on
Unusual pump noise on a cold start
Usually no change in driving

What could be wrong

1Air pump seized by moisture or burnt out
2Check valve stuck
3Hose loose or cracked
4Pump relay or fuse

Repair difficulty: Moderate

What you can check yourself

On a cold start, listen for the pump droning in the engine bay for a few seconds. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

We check pump and valve operation with the diagnostic tool
We check the hoses and relay
We replace the pump or valve

Standard SAE description: Secondary Air Injection System Insufficient Flow Bank 1

This code usually comes with: Check engine lightSee what the light means →

Want a definite answer?

Bring the car to our workshop in Estonia for diagnostics. We read the fault codes, test the sensors and tell you what is wrong. Repair price depends on the work involved, generally €45 per hour.

Book a diagnostic check

Questions

What does fault code P0491 mean?

Secondary air system: flow too low (bank 1). The secondary air system blows air into the exhaust on a cold start so the catalytic converter warms up faster. The computer found too little air or a fault in the pump or valve control.

Can I drive with code P0491?

OK to drive, but have it checked soon.

How much does it cost to fix P0491?

Roughly €80–600 in Estonia. The price depends on exactly what has failed and on the car.

How is P0491 fixed?

We check pump and valve operation with the diagnostic tool. We check the hoses and relay. We replace the pump or valve.

Based on AI combined with our hands-on workshop experience and knowledge. This information is general and prices are approximate (Estonian workshop rates). The same code can mean different things on different cars. Only an inspection of the car gives a definite answer.