BMW DTC P0139 – O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
DTC P0139 meaning on BMW
The Diagnostic Trouble Code (DTC) P0139 for BMW indicates an issue with the O2 sensor circuit slow response for Bank 1 Sensor 2. This means that the downstream oxygen sensor in Bank 1 is not responding as quickly as expected by the Engine Control Module (ECM).
BMW DTC P0139 symptoms
Symptoms of DTC P0139 on a BMW may include:
- Check Engine Light (CEL) illuminated on the dashboard
- Poor fuel economy
- Engine running rough or misfiring
- Increased emissions
BMW DTC P0139 causes
Common causes of DTC P0139 on a BMW include:
- Failed or deteriorated downstream O2 sensor
- Wiring or connector issues in the O2 sensor circuit
- Exhaust leaks near the downstream O2 sensor
- ECM software issues
BMW DTC P0139 seriousness
While DTC P0139 may not cause immediate drivability issues, it can lead to poor engine performance and increased emissions if left unresolved. It is important to address this code promptly to prevent further damage to the vehicle and ensure optimal fuel efficiency.
How to diagnose DTC P0139 on BMW
To diagnose DTC P0139 on a BMW, you can follow these steps:
- Use an OBD-II scanner to retrieve the specific fault code
- Inspect the downstream O2 sensor and its wiring for any visible damage
- Check for exhaust leaks near the downstream O2 sensor
- Perform a voltage test on the O2 sensor circuit to check for proper response
How to fix DTC P0139 on BMW
To fix DTC P0139 on a BMW, you can try the following solutions:
- Replace the downstream O2 sensor with a new, OEM-quality sensor
- Repair any damaged wiring or connectors in the O2 sensor circuit
- Fix any exhaust leaks near the downstream O2 sensor
- If necessary, update the ECM software to address any software-related issues
How to erase DTC P0139 on BMW
To erase DTC P0139 on a BMW, you can clear the fault code using an OBD-II scanner. After addressing the underlying issue causing the fault code, you can reset the ECM by clearing the code and performing a drive cycle to ensure the code does not return.
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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