P21C3
Reductant Heater Relay Control Circuit Low
P21C3 is an OBD-II diagnostic trouble code meaning: Reductant Heater Relay Control Circuit Low. Common causes: open or short circuit in heater relay circuit, faulty reagent heater relay. Estimated repair cost: $9–39.
Symptoms
- Check Engine light comes on
- Reduced efficiency of the SCR system
- Possible increase in NOx emissions
- In some cases - limiting engine power
- AdBlue system error message on the dashboard
Causes
- Open or short circuit in heater relay circuit
- Faulty reagent heater relay
- Connection problems or connector corrosion
- SCR control unit malfunction
- Wiring Harness Problems
How to Fix
- Check fuses associated with the SCR system
- Inspect the wiring and connectors of the heater relay circuit
- Check the resistance and operation of the heater relay
- Scan the system for additional trouble codes
- Replace the reagent heater relay if necessary.
Related codes
Error P21C3 by Vehicle Brand
FAQ
What does the P21C3 code mean?
P21C3 is an OBD-II diagnostic trouble code that indicates: Reductant Heater Relay Control Circuit Low
What causes a P21C3 error code?
The most common causes of P21C3 include: Open or short circuit in heater relay circuit; Faulty reagent heater relay; Connection problems or connector corrosion; SCR control unit malfunction.
How do I fix a P21C3 diagnostic trouble code?
To fix P21C3: Check fuses associated with the SCR system. Inspect the wiring and connectors of the heater relay circuit. Check the resistance and operation of the heater relay. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with P21C3?
Yes, but get it checked soon
How much does it cost to fix P21C3?
The estimated repair cost for P21C3 is $9–39. Actual cost depends on your vehicle, location, and labor rates.
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