P125B – BMW DTC

BMW DTC P125B – NOx Sensor Heater Control Circuit Heater Output Too Low During Operation (Bank 1)

DTC P125B meaning on BMW

DTC P125B on a BMW indicates that the NOx (Nitrogen Oxide) sensor heater control circuit’s heater output is too low during operation in Bank 1. This means that the heating element in the NOx sensor is not functioning properly, which can affect the sensor’s ability to accurately measure the level of NOx emissions in the exhaust gases.

BMW DTC P125B symptoms

Symptoms of DTC P125B on a BMW may include:

• Check Engine Light (MIL) illuminated
• Reduced engine performance
• Increased fuel consumption
• Possible emission of higher levels of NOx

BMW DTC P125B causes

Common causes of DTC P125B on a BMW include:

• Failed NOx sensor heater
• Wiring or connector issues in the sensor circuit
• Faulty engine control module (ECM)

BMW DTC P125B seriousness

DTC P125B should not be ignored as it can lead to increased emissions of harmful NOx gases, which can have negative environmental impacts. Additionally, prolonged operation with this fault may affect the vehicle’s performance and fuel efficiency.

How to diagnose DTC P125B on BMW

To diagnose DTC P125B on a BMW, you can perform the following steps:

1. Use a diagnostic scanner to retrieve the fault codes and freeze frame data
2. Inspect the NOx sensor and its wiring for any visible damage or corrosion
3. Check the sensor heater circuit for continuity and proper voltage supply
4. Test the NOx sensor heater resistance to determine if it is within specifications

How to fix DTC P125B on BMW

To fix DTC P125B on a BMW, you may need to:

1. Replace the faulty NOx sensor with a new one
2. Repair any damaged wiring or connectors in the sensor circuit
3. Check and replace the engine control module (ECM) if necessary

How to erase DTC P125B on BMW

To erase DTC P125B on a BMW, you can:

1. Use a diagnostic scanner to clear the fault codes
2. After making the necessary repairs, perform a test drive to ensure the issue is resolved

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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