P21AF – BMW DTC

BMW DTC P21AF – Reductant Level Sensor ‘C’ Circuit Low

DTC P21AF meaning on BMW

The DTC P21AF on a BMW indicates a fault with the Reductant Level Sensor ‘C’ circuit. This sensor is responsible for monitoring the level of the diesel exhaust fluid (DEF), also known as AdBlue, in the vehicle’s tank. A low circuit signal suggests that the sensor is detecting a lower-than-expected level of DEF.

BMW DTC P21AF symptoms

Symptoms of the DTC P21AF on a BMW may include:

• Check Engine Light illuminated
• Reduced engine performance
• Possible DEF warning message on the instrument cluster

BMW DTC P21AF causes

Common causes of the DTC P21AF on a BMW include:

• Defective Reductant Level Sensor ‘C’
• Wiring or connector issues in the sensor circuit
• Low DEF fluid level in the tank

BMW DTC P21AF seriousness

While the DTC P21AF may not cause immediate drivability issues, it is important to address this fault promptly to ensure proper emissions control and compliance with environmental regulations. Ignoring the issue could lead to increased emissions and potential engine performance issues.

How to diagnose DTC P21AF on BMW

To diagnose the DTC P21AF on a BMW, a mechanic may perform the following steps:

1. Use a diagnostic scanner to retrieve the fault code and related data
2. Inspect the Reductant Level Sensor ‘C’ and its wiring for any visible damage or corrosion
3. Check the DEF fluid level in the tank
4. Perform a circuit test to verify the sensor’s functionality

How to fix DTC P21AF on BMW

To fix the DTC P21AF on a BMW, the following steps may be taken:

1. Replace the Reductant Level Sensor ‘C’ if it is found to be faulty
2. Repair any damaged wiring or connectors in the sensor circuit
3. Refill the DEF tank with the appropriate fluid if the level is low
4. Clear the fault code and perform a test drive to ensure the issue is resolved

How to erase DTC P21AF on BMW

To erase the DTC P21AF on a BMW, a diagnostic scanner can be used to clear the fault code from the vehicle’s memory. After addressing the underlying issue and making the necessary repairs, the fault code can be reset to turn off the Check Engine Light and ensure proper operation of the emissions system.

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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