P0491 BMW Code - AIR System Insufficient Flow Bank 1
Quick Answer
The AIR system refers to an emissions control system. Common causes include Secondary Air Injection Valve blocked, Faulty Secondary Air Injection Valve, Faulty Secondary Air Injection Pump. 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 BMW indicates AIR System Insufficient Flow Bank 1.
- Common causes
- Common causes include Secondary Air Injection Valve blocked, Faulty Secondary Air Injection Valve, Faulty Secondary Air Injection Pump.
- 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.
Code P0491 BMW Description
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.
What are the Possible Causes of the DTC P0491 BMW?
- Secondary Air Injection Valve blocked
- Faulty Secondary Air Injection Valve
- Faulty Secondary Air Injection Pump
How to Fix the DTC P0491 BMW?
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 BMW 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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Frequently Asked Questions about P0491 BMW Code
1. What does the OBDII code P0491 mean on a BMW?
P0491 indicates "AIR System Insufficient Flow Bank 1," meaning the secondary air injection system isn't providing enough airflow to the exhaust on Bank 1.
2. What are the common symptoms of P0491 in a BMW?
Symptoms include an illuminated Check Engine Light, rough cold starts, increased emissions, and possible failed emissions tests.
3. What causes the P0491 code to appear on a BMW?
Common causes include a faulty secondary air pump, clogged air injection valves, damaged hoses, or carbon buildup in the exhaust ports.
4. Can a faulty secondary air pump trigger the P0491 code?
Yes, a failing or non-functional secondary air pump is one of the primary causes of insufficient airflow in the secondary air system.
5. How do I diagnose the P0491 code on a BMW?
Start by inspecting the secondary air pump, check valves, and hoses for damage or blockages. Use a scan tool and smoke test to confirm the airflow issue.
6. Is it safe to drive with a P0491 code on my BMW?
It’s generally safe to drive, but the car may produce higher emissions, fail a smog test, or have reduced performance during cold starts.
7. How much does it typically cost to fix the P0491 code on a BMW?
Repair costs vary but can range from $200 to $800 depending on whether the issue is with the air pump, valves, or hoses.
8. Can cleaning the air injection system fix the P0491 code?
Yes, cleaning carbon buildup in the system, including the exhaust ports and check valves, can often resolve the issue.
9. What happens if the P0491 code is ignored?
Ignoring the code can lead to higher emissions, potential damage to the air injection system, and difficulty passing emissions tests.
10. Can a bad relay or fuse cause the P0491 code in a BMW?
Yes, a faulty relay or blown fuse can prevent the secondary air pump from functioning, leading to insufficient airflow and triggering the code.
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