P21C9
Reductant Control Module Power Relay/Relays Control Circuit High
P21C9 is an OBD-II diagnostic trouble code meaning: Reductant Control Module Power Relay/Relays Control Circuit High. Common causes: faulty reagent control module relay, short circuit in control circuit. Estimated repair cost: $17–89.
Symptoms
- Check Engine light comes on
- Reduced engine power
- Increased fuel consumption
- Problems with the SCR system
- Possible engine operation restrictions
Causes
- Faulty reagent control module relay
- Short circuit in control circuit
- Wiring harness damage
- Problems with the SCR ECU
- Corrosion of contacts or connectors
How to Fix
- Check the condition of the reagent control module relay
- Check the integrity of wiring and connectors
- Measure the voltage in the control circuit
- Check the operation of the reagent control module
- If necessary, replace faulty components
Related codes
Error P21C9 by Vehicle Brand
FAQ
What does the P21C9 code mean?
P21C9 is an OBD-II diagnostic trouble code that indicates: Reductant Control Module Power Relay/Relays Control Circuit High
What causes a P21C9 error code?
The most common causes of P21C9 include: Faulty reagent control module relay; Short circuit in control circuit; Wiring harness damage; Problems with the SCR ECU.
How do I fix a P21C9 diagnostic trouble code?
To fix P21C9: Check the condition of the reagent control module relay. Check the integrity of wiring and connectors. Measure the voltage in the control circuit. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with P21C9?
Yes, but get it checked soon
How much does it cost to fix P21C9?
The estimated repair cost for P21C9 is $17–89. Actual cost depends on your vehicle, location, and labor rates.
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