P21CB
Reductant Control Module Supply Voltage Low
P21CB is an OBD-II diagnostic trouble code meaning: Reductant Control Module Supply Voltage Low. Common causes: damage to the wiring harness to the module, blown power fuse. Estimated repair cost: $56–278.
Symptoms
- Check Engine Light Is On
- Reduced engine power
- Possible SCR error messages
- Increased NOx emissions
- AdBlue system may stop working
Causes
- Damage to the wiring harness to the module
- Blown power fuse
- Poor contact in connectors
- Reagent control module malfunction
- Problems with the module power relay
How to Fix
- Check the module power supply fuses
- Inspect the wiring harness for damage
- Check connections and contacts in connectors
- Measure the voltage at the module terminals
- If necessary, replace the reagent control module
Related codes
Error P21CB by Vehicle Brand
FAQ
What does the P21CB code mean?
P21CB is an OBD-II diagnostic trouble code that indicates: Reductant Control Module Supply Voltage Low
What causes a P21CB error code?
The most common causes of P21CB include: Damage to the wiring harness to the module; Blown power fuse; Poor contact in connectors; Reagent control module malfunction.
How do I fix a P21CB diagnostic trouble code?
To fix P21CB: Check the module power supply fuses. Inspect the wiring harness for damage. Check connections and contacts in connectors. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with P21CB?
Limited driving only, diagnose soon
How much does it cost to fix P21CB?
The estimated repair cost for P21CB is $56–278. Actual cost depends on your vehicle, location, and labor rates.
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