The OBD code P0491 for Audi indicates a Secondary Air Injection System Insufficient Flow (Bank 1).
This affects the AIR system.
Symptoms include the Engine Light being ON.
Causes can be an intake leak, damaged AIR system components, faulty AIR Solenoid Valve, or a faulty AIR system relay.
It’s a moderate issue.
A possible fix is to inspect the wiring harness, connectors, and components for damage.
Repair Importance Level | 6.67 (Out of 10) |
Estimated Repair Time | Approximately 1.0 hour |
Repair Difficulty Level | 6.67 (Out of 10) |
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Symptoms of the Audi p0491 OBD Code
The Audi P0491 fault code typically triggers when there is an issue with the secondary air injection system.
- Symptoms: Engine Light ON (or Service Engine Soon Warning Light).
- Reduced engine performance.
- Increased fuel consumption.
- Possible rattling noise from the engine compartment.
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Causes of the Audi p0491 OBD Code
P0491 in Audi indicates a fault in the secondary air injection system, affecting air flow.
- P0491 can be caused by an intake leak.
- Damaged AIR system components.
- Faulty AIR Solenoid Valve.
- Faulty AIR system relay.
Fixing Audi Error Code p0491 Step By Step
Replace faulty secondary air injection system relay in Audi with fault code P0491.
- To fix Audi OBDII code P0491, start by reviewing the possible causes related to the secondary air injection system.
- Visually inspect the wiring harness and connectors for any damage or corrosion.
- Check the connector pins for any signs of being broken, bent, pushed out, or corroded.
- Test the secondary air injection pump and associated components for proper operation.
- Replace any faulty components such as the secondary air injection pump, relay, or fuse if necessary.
- Clear the fault code and perform a test drive to ensure the issue has been resolved.
Cost Of Fixing Audi p0491 Fault Code
The repair for Audi fault code P0491 typically involves replacing the secondary air injection system relay.
The cost to diagnose and fix Audi OBD code P0491 depends on the estimated 1. 0hour repair time.
Labor rates range from $75 to $150 per hour, so the general cost could be between $75 and $150. The final cost may vary based on shop rates and the complexity of the repair.
Details of the Audi p0491 OBD Code
Audi P0491 indicates a Secondary Air Injection System Insufficient Flow Bank 1.
OBD code P0491 for Audi vehicles indicates a Secondary Air Injection System Insufficient Flow Bank 1. This code is triggered by the Engine Control Module (ECM) when it detects that the flow of air injected into the exhaust system to reduce emissions is not at the expected level in Bank 1 of the engine.
The Secondary Air Injection System helps reduce harmful emissions during cold starts by introducing fresh air into the exhaust system.
If the flow is insufficient, it can lead to increased emissions output.
Mechanic’s Tech Notes
Detailed information on Audi fault code P0491, Secondary Air Injection System Insufficient Flow Bank 1.
To diagnose and fix OBDII code P0491 in an Audi, start by visually inspecting the wiring harness and connectors related to the secondary air injection system.
Look for any damage or corrosion.
Use a voltmeter to check the power and ground connections to the secondary air injection pump.
Ensure the pump is receiving the correct voltage when activated.
Scan tools can help monitor the pump’s operation and check for any faults in the system.
If necessary, clean or replace any damaged components, repair wiring issues, or replace the secondary air injection pump to resolve the P0491 fault code.
FAQ
Common symptoms for OBD code P0491 in an Audi include Engine Light ON, caused by intake leak, damaged AIR system components, faulty AIR Solenoid Valve, or relay.
The typical root cause of OBD code P0491 in Audi vehicles is a faulty AIR Solenoid Valve or damaged AIR system components.
To diagnose and repair OBD code P0491 in your Audi for Engine Light ON, check for intake leaks, damaged AIR system parts, faulty AIR Solenoid Valve, and relay. Inspect wiring and connectors.

Wrap Up
If your Audi is displaying OBD code P0491, you may experience poor engine performance, increased emissions, or a rough idle.
This code typically indicates a fault in the secondary air injection system, possibly caused by a faulty air pump, damaged hoses, or a malfunctioning secondary air injection pump relay.
To address Audi OBD code P0491, start by inspecting the secondary air injection system components such as the air pump, hoses, and relay for any signs of damage or wear.
Test the electrical connections and wiring harness for proper continuity and repair or replace any faulty parts as needed.