What does code P21CA mean?

Q: What does code P21CA mean?

Reductant Control Module Supply Voltage Circuit. P21CA indicates that the reductant control module has detected an abnormal supply voltage on its power circuit, typically outside the expected 9–16 volt range. The module monitors its own feed and sets this code when the voltage is too low, too high, or intermittent, which can disable the selective catalytic reduction (SCR) system and illuminate the warning light.

DTC codes / P21xx · Fuel and air metering / P21CA

P21CAReductant Control Module Supply Voltage Circuit

P21CA indicates that the reductant control module has detected an abnormal supply voltage on its power circuit, typically outside the expected 9–16 volt range. The module monitors its own feed and sets this code when the voltage is too low, too high, or intermittent, which can disable the selective catalytic reduction (SCR) system and illuminate the warning light.

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.