P21C7 – BMW DTC

BMW DTC P21C7 – Reductant Control Module Power Relay/Relays Control Circuit/Open

DTC P21C7 meaning on BMW

The Diagnostic Trouble Code (DTC) P21C7 for BMW refers to an issue with the Reductant Control Module Power Relay/Relays Control Circuit being open. This fault code indicates a problem with the power relay or relays that control the Reductant Control Module in the vehicle’s emissions system.

BMW DTC P21C7 symptoms

Symptoms of the DTC P21C7 on a BMW may include:

• Check Engine Light illuminated on the dashboard
• Reduced engine performance
• Possible decrease in fuel efficiency

BMW DTC P21C7 causes

Common causes of the DTC P21C7 on a BMW include:

• Faulty Reductant Control Module Power Relay
• Open or short circuit in the relay control circuit
• Wiring issues or poor connections

BMW DTC P21C7 seriousness

The DTC P21C7 should be addressed promptly as it can affect the vehicle’s emissions system and overall performance. Ignoring this fault code may lead to increased emissions, reduced fuel efficiency, and potential damage to other components in the emissions system.

How to diagnose DTC P21C7 on BMW

To diagnose the DTC P21C7 on a BMW, a mechanic would typically perform the following steps:

1. Use a diagnostic scanner to retrieve the fault code and related data
2. Inspect the Reductant Control Module Power Relay for any visible damage
3. Check the relay control circuit for continuity and proper voltage
4. Inspect wiring and connections for any signs of wear or corrosion

How to fix DTC P21C7 on BMW

To fix the DTC P21C7 on a BMW, the following steps may be taken:

1. Replace the faulty Reductant Control Module Power Relay
2. Repair any open or short circuits in the relay control circuit
3. Ensure all wiring and connections are secure and free of damage
4. Clear the fault code and perform a test drive to verify the repair

How to erase DTC P21C7 on BMW

To erase the DTC P21C7 on a BMW, a diagnostic scanner can be used to clear the fault code from the vehicle’s memory. After the repair has been completed and the issue resolved, the code can be erased to reset the Check Engine Light and ensure the fault does not reoccur.

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

Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.