P21C8
Reductant Control Module Power Relay/Relays Control Circuit Low
P21C8 is an OBD-II diagnostic trouble code meaning: Reductant Control Module Power Relay/Relays Control Circuit Low. Common causes: faulty regenerator module relay, open or short circuit in control circuit. Estimated repair cost: $28–167.
Symptoms
- Check Engine light comes on
- Reduced engine power (in some cases)
- Increased NOx emissions
- SCR system error message on dashboard
- AdBlue system malfunction
Causes
- Faulty regenerator module relay
- Open or short circuit in control circuit
- Poor contact in connectors
- Reducer module malfunction
- Problems with the engine control unit
How to Fix
- Check the regenerator module relay
- Inspect the control circuit for damage
- Check connections and connectors
- Test the reducer module
- Check power and ground circuit
- If necessary, replace the relay or module
Related codes
Error P21C8 by Vehicle Brand
FAQ
What does the P21C8 code mean?
P21C8 is an OBD-II diagnostic trouble code that indicates: Reductant Control Module Power Relay/Relays Control Circuit Low
What causes a P21C8 error code?
The most common causes of P21C8 include: Faulty regenerator module relay; Open or short circuit in control circuit; Poor contact in connectors; Reducer module malfunction.
How do I fix a P21C8 diagnostic trouble code?
To fix P21C8: Check the regenerator module relay. Inspect the control circuit for damage. Check connections and connectors. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with P21C8?
Yes, but get it checked soon
How much does it cost to fix P21C8?
The estimated repair cost for P21C8 is $28–167. Actual cost depends on your vehicle, location, and labor rates.
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