BMW DTC P21C3 – Reductant Heater Relay Control Circuit Low
DTC P21C3 meaning on BMW
The Diagnostic Trouble Code (DTC) P21C3 for BMW refers to the ¨Reductant Heater Relay Control Circuit Low.¨ This code indicates that the control circuit for the reductant heater relay is operating at a lower voltage level than expected.
BMW DTC P21C3 symptoms
Symptoms of the BMW DTC P21C3 may include:
- Check Engine Light (MIL) illuminated
- Reduced engine performance
- Possible DEF (Diesel Exhaust Fluid) system warnings
BMW DTC P21C3 causes
Common causes of the BMW DTC P21C3 may include:
- Defective reductant heater relay
- Wiring issues in the reductant heater relay circuit
- Faulty reductant heater
BMW DTC P21C3 seriousness
The seriousness of the BMW DTC P21C3 code lies in its potential impact on emissions control and engine performance. Ignoring this code may lead to increased emissions, reduced fuel efficiency, and potential damage to the exhaust aftertreatment system.
How to diagnose DTC P21C3 on BMW
To diagnose the DTC P21C3 on a BMW, you can follow these steps:
- Use a diagnostic scanner to retrieve the fault codes.
- Inspect the reductant heater relay and its wiring for any visible damage.
- Test the reductant heater relay and circuit for proper voltage and continuity.
How to fix DTC P21C3 on BMW
To fix the DTC P21C3 on a BMW, you may need to:
- Replace the faulty reductant heater relay.
- Repair any damaged wiring in the reductant heater relay circuit.
- If the reductant heater is faulty, replace it with a new one.
How to erase DTC P21C3 on BMW
To erase the DTC P21C3 on a BMW, you can:
- Use a diagnostic scanner to clear the fault codes.
- After fixing the underlying issue, clear the code again to ensure it does not return.
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.