BMW DTC P0491 – AIR System Insufficient Flow (Bank 1)
DTC P0491 meaning on BMW
The Diagnostic Trouble Code (DTC) P0491 for BMW indicates an AIR System Insufficient Flow in Bank 1. This means that there is a problem with the secondary air injection system, which is responsible for reducing emissions during cold starts by injecting fresh air into the exhaust system.
BMW DTC P0491 symptoms
Symptoms of DTC P0491 on a BMW may include:
- Check Engine Light illuminated on the dashboard
- Reduced engine performance
- Increased emissions
- Possible rough idling or stalling
BMW DTC P0491 causes
Common causes of DTC P0491 on a BMW include:
- Faulty air pump
- Blocked or leaking air hoses
- Malfunctioning air pump relay
- Issues with the air pump control module
BMW DTC P0491 seriousness
While DTC P0491 may not cause immediate drivability issues, it can lead to increased emissions and potential long-term damage to the vehicle’s emissions control system. It is important to address this issue promptly to ensure optimal engine performance and reduce environmental impact.
How to diagnose DTC P0491 on BMW
To diagnose DTC P0491 on a BMW, you can perform the following steps:
- Use an OBD-II scanner to retrieve the fault code and freeze frame data
- Inspect the air pump, air hoses, and related components for any visible damage or leaks
- Check the air pump relay and control module for proper operation
- Perform a smoke test to identify any air leaks in the system
How to fix DTC P0491 on BMW
To fix DTC P0491 on a BMW, you can try the following solutions:
- Replace the faulty air pump if it is found to be defective
- Repair or replace any damaged or leaking air hoses
- Test and replace the air pump relay or control module if necessary
- Clear any obstructions in the air injection system
How to erase DTC P0491 on BMW
After addressing the underlying issue causing DTC P0491 on a BMW, you can erase the fault code using an OBD-II scanner. Simply clear the code from the vehicle’s computer system to reset the Check Engine Light and ensure that the repair was successful.
Recommended tools & DTC Scanners for BMW
Best Diagnostic App for modern BMWs: BimmerLink
Recommended Bluetooth adapter for Bimmerlink: OBDLink CX
Cable adapter for Bimmerlink: Enet Cable USB Type C
For older BMWs we recommend: Autel AutoLink AL319 (2024 version)
Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter
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