BMW DTC P21AD – Reductant Level Sensor ‘C’ Circuit
DTC P21AD meaning on BMW
The DTC P21AD fault code on a BMW indicates an issue with the Reductant Level Sensor ‘C’ circuit. This sensor is responsible for monitoring the level of the diesel exhaust fluid (DEF) in the vehicle’s selective catalytic reduction (SCR) system.
BMW DTC P21AD symptoms
Symptoms of the DTC P21AD code on a BMW may include:
- Check Engine Light illuminated
- Reduced engine performance
- Possible DEF fluid level warning message
BMW DTC P21AD causes
Common causes of the DTC P21AD fault code on a BMW include:
- Defective Reductant Level Sensor ‘C’
- Wiring or connector issues in the sensor circuit
- Low DEF fluid level
BMW DTC P21AD seriousness
The DTC P21AD code should not be ignored as it can lead to increased emissions and potential damage to the vehicle’s emissions control system. It is recommended to address this issue promptly to ensure proper vehicle operation.
How to diagnose DTC P21AD on BMW
To diagnose the DTC P21AD code on a BMW, a mechanic may perform the following steps:
- Use a diagnostic scanner to retrieve the fault code and related data
- Inspect the Reductant Level Sensor ‘C’ and its wiring for any visible damage
- Check the DEF fluid level and quality
- Perform a circuit test to verify sensor functionality
How to fix DTC P21AD on BMW
To fix the DTC P21AD fault code on a BMW, the following steps may be taken:
- Replace the Reductant Level Sensor ‘C’ if found to be faulty
- Repair any damaged wiring or connectors in the sensor circuit
- Refill DEF fluid to the appropriate level
- Clear the fault code and perform a test drive to ensure the issue is resolved
How to erase DTC P21AD on BMW
To erase the DTC P21AD fault code on a BMW, a diagnostic scanner can be used to clear the code from the vehicle’s engine control module. Once the fault code is cleared, the Check Engine Light should turn off. It is important to verify that the issue has been resolved before clearing the code.
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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