P21C3 - Reductant Heater Relay Control Circuit Low
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2022 Ford F-550 Super Duty, 2022 Ford F-450 Super Duty, 2022 Ford F-350 Super Duty, 2022 Ford F-250 Super Duty, and 2021 Ford F-550 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
DTC DESCRIPTION P21C3 - REDUCTANT HEATER RELAY CONTROL CIRCUIT LOW
| Description: The PCM enables the Glow Plug Control Module (GPCM) during a self-test which monitors the RDHTRCTRL circuit. When the GPCM detects that the RDHTRCTRL circuit is drawing greater than 6 amps for greater than 250 milliseconds, a short to ground is suspect. The GPCM sends a message to the PCM, which sets this DTC. | |||
Possible Causes:
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| 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 . | ||