What does code P21CC mean?

Q: What does code P21CC mean?

Reductant Control Module Supply Voltage High. P21CC indicates that the reductant control module has detected a supply voltage that is higher than the manufacturer's specified range, typically above 16 volts. The module monitors its power input and sets this code when the voltage exceeds the expected threshold, which can disrupt the precise control of the diesel exhaust fluid (DEF) system.

DTC codes / P21xx · Fuel and air metering / P21CC

P21CCReductant Control Module Supply Voltage High

P21CC indicates that the reductant control module has detected a supply voltage that is higher than the manufacturer's specified range, typically above 16 volts. The module monitors its power input and sets this code when the voltage exceeds the expected threshold, which can disrupt the precise control of the diesel exhaust fluid (DEF) system.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.