What does code P21C7 mean?

Q: What does code P21C7 mean?

Reductant Control Module Power Relay Control Circuit/Open. P21C7 indicates that the reductant control module has detected an open circuit in the power relay control circuit, meaning the module cannot energize or verify the relay that supplies power to the diesel exhaust fluid (DEF) system. The computer monitors the control wire for expected voltage changes when the relay is commanded on or off, and it sets this code when the circuit remains open or fails to respond.

DTC codes / P21xx · Fuel and air metering / P21C7

P21C7Reductant Control Module Power Relay Control Circuit/Open

P21C7 indicates that the reductant control module has detected an open circuit in the power relay control circuit, meaning the module cannot energize or verify the relay that supplies power to the diesel exhaust fluid (DEF) system. The computer monitors the control wire for expected voltage changes when the relay is commanded on or off, and it sets this code when the circuit remains open or fails to respond.

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.