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p0491
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BMW · Sedans
Secondary Air Injection System Insufficient Flow Bank 1
Quick Answer
Error code P0491 on your BMW Sedans means: Secondary Air Injection System Insufficient Flow Bank 1. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
330i530i540i740i760i330e 2024330i xDrive 2024530i 2024530i xDrive 2024540i xDrive 2024545e xDrive 2024740i 2024740i xDrive 2024760i xDrive 2024M3 CS 2024M3 Competition 2024M3 Competition xDrive 2024M340i xDrive 2024i4 M50 2024i4 eDrive35 2024i4 eDrive40 2024M3M340ii4i5
Likely Causes
  1. Failed secondary air injection pump
  2. Clogged secondary air injection check valve
  3. Carbon buildup in the cylinder head air passages
  4. Damaged secondary air pump relay
  5. Cracked or disconnected secondary air hoses
How to Fix It
1
Activate the secondary air pump via scan tool and listen for operation
2
Inspect secondary air pump relay and fuse
3
Check secondary air check valves for carbon buildup or seizure
4
Inspect all secondary air hoses for cracks and proper connection
5
Replace secondary air pump if airflow output is insufficient
Pro Tip
This issue typically requires professional diagnosis. Attempting this fix without proper training could cause further problems.
Parts You May Need
Secondary air injection pump
Secondary air check valve
Secondary air pump relay
Secondary air hoses
Related Error Codes
P0171P0174P0300P0335P0340
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