BMW DTC P125C – NOx Sensor Heater Control Circuit Heater Supply Voltage (Bank 1)
DTC P125C meaning on BMW
DTC P125C for BMW refers to a fault in the NOx (Nitrogen Oxide) sensor heater control circuit’s heater supply voltage on Bank 1. This diagnostic trouble code indicates that there is an issue with the electrical circuit responsible for supplying power to the NOx sensor heater on Bank 1 in the vehicle.
BMW DTC P125C symptoms
Symptoms of DTC P125C on a BMW may include:
- Check Engine Light (MIL) illuminated
- Reduced engine performance
- Increased emissions
- Possible decrease in fuel efficiency
BMW DTC P125C causes
Common causes of DTC P125C on a BMW include:
- Faulty NOx sensor heater
- Wiring or connector issues in the NOx sensor heater circuit
- Blown fuse related to the NOx sensor heater
- ECU (Engine Control Unit) malfunction
BMW DTC P125C seriousness
The seriousness of DTC P125C on a BMW lies in the potential impact on emissions and engine performance. Ignoring this fault can lead to increased emissions, reduced fuel efficiency, and potential long-term damage to the vehicle’s engine and emission control systems.
How to diagnose DTC P125C on BMW
To diagnose DTC P125C on a BMW, you can follow these steps:
- Use an OBD-II scanner to retrieve the fault code and freeze frame data
- Inspect the wiring and connectors related to the NOx sensor heater
- Check the NOx sensor heater for proper operation
- Test the fuse related to the NOx sensor heater
- Perform a continuity test on the circuit to identify any open or short circuits
How to fix DTC P125C on BMW
To fix DTC P125C on a BMW, you can consider the following actions:
- Replace the faulty NOx sensor heater
- Repair or replace any damaged wiring or connectors in the circuit
- Replace the blown fuse with the correct rating
- If the ECU is faulty, consider reprogramming or replacing it
How to erase DTC P125C on BMW
To erase DTC P125C on a BMW, you can use an OBD-II scanner to clear the fault code after the underlying issue has been resolved. Once the repair or replacement of components related to the NOx sensor heater circuit is completed, you can clear the code to reset the Check Engine Light and monitor the system for any recurring faults.
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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