DTC P21C7 - Reductant Control Module Power Relay Control Circuit Open

DTC DESCRIPTION P21C7 - REDUCTANT CONTROL MODULE POWER RELAY CONTROL CIRCUIT OPEN

Description:	The PCM carries out a functional key ON, engine running (KOER) self-test for the glow plug system. During that test, the PCM enables the glow plug control module (GPCM) which monitors each individual reductant heater and harness for concerns. When the GPCM detects a concern with a reductant heater relay or the RDHTRPWR circuit, the GPCM sends a message to the PCM which sets this DTC.
Possible Causes:	Damaged reductant heater relay RDHTRPWR circuit open RDHTRPWR circuit short to ground RDHTRPWR circuit short to voltage
Diagnostic Aids:	The presence of this DTC may indicate that the vehicle is operating in derate mode and may experience a loss of power. After repair, the vehicle may still display a system warning message. Drive the vehicle until the system warning message has cleared from the instrument cluster message center.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
All	GO to PINPOINT TEST RH .