AutoCodes – Audi – P0491 Audi

P0491 Audi Code - Secondary Air Injection System Insufficient Flow Bank 1

Quick Answer

The AIR system refers to an emissions control system used by some vehicle manufacturers. Common causes include Intake leak, Damaged AIR system components, Faulty AIR Solenoid Valve. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P0491 Audi indicates Secondary Air Injection System Insufficient Flow Bank 1.
Common causes: Common causes include Intake leak, Damaged AIR system components, Faulty AIR Solenoid Valve.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

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Code Popularity 19,778

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 12, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0491 Audi Description

The AIR system refers to an emissions control system used by some vehicle manufacturers. It is often called Secondary Air Injection, because air, more specifically oxygen, is injected into the exhaust manifold after startup. Vehicles start on a comparatively rich mixture to allow for smoother running conditions. However, this has a large impact on exhaust gas emissions. A notable increase in hydrocarbon (HC) and carbon monoxide (CO) emissions are found under these rich start conditions. By injecting air into the exhaust manifold the CO and HC can be oxidized. This reaction increases the temperature within the exhaust and the exhaust gas after-treatment system i.e. catalytic converter can begin working earlier due to meeting its light-off temperature.
The system consists of an air pump, a one-way check valve and associated pipework. The system operates for a predetermined time after startup. Normally this duration is approximately three minutes, when cold.

OBDII Code P0491 Audi - Secondary Air Injection System Insufficient Flow Bank 1 - AutoCodes.com — P0491 Audi Code - Secondary Air Injection System Insufficient Flow Bank 1

What does this mean?

What are the Possible Causes of the DTC P0491 Audi?

Intake leak
Damaged AIR system components
Faulty AIR Solenoid Valve
Faulty AIR system relay

How to Fix the DTC P0491 Audi?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0491 Audi code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0491 Audi Code

1. What does the OBDII code P0491 mean on an Audi?

P0491 indicates "Secondary Air Injection System Insufficient Flow Bank 1," meaning the secondary air injection system is not functioning properly on the engine's Bank 1.

2. What are the common symptoms of the P0491 code in an Audi?

Symptoms may include a check engine light, failed emissions tests, rough cold starts, and reduced engine performance.

3. What causes the P0491 code in an Audi?

Common causes include a faulty secondary air pump, clogged or leaking air injection hoses, a defective check valve, or issues with the secondary air injection relay or wiring.

4. How does the secondary air injection system work in an Audi?

The system pumps fresh air into the exhaust during cold starts to reduce emissions by helping the catalytic converter reach operating temperature faster.

5. Can a clogged air injection hose trigger the P0491 code?

Yes, a clogged or restricted hose can prevent proper air flow, causing the system to detect insufficient air injection.

6. Is it safe to drive an Audi with the P0491 code?

While it may be safe to drive short-term, ignoring the issue can lead to increased emissions, potential damage to the catalytic converter, and failed emissions inspections.

7. How can I diagnose the P0491 code in my Audi?

Diagnose by checking the secondary air pump operation, inspecting hoses and valves for clogs or leaks, and testing the relay and electrical connections for faults.

8. What is the most common repair for the P0491 code on an Audi?

The most common repair is replacing the secondary air pump or cleaning/replacing a clogged check valve.

9. How much does it typically cost to fix the P0491 code in an Audi?

Repair costs vary but can range from $150 to $700, depending on whether the issue is a simple hose replacement, valve cleaning, or air pump replacement.

10. How can I prevent the P0491 code from recurring in my Audi?

Regular maintenance, such as inspecting hoses and valves for blockages and ensuring proper system operation, can help prevent this code from reappearing.