# P21C4 on the 2019 Ram 2500

The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.

Nobody has written a description of this code yet.

## Bulletins for this model year that name P21C4

- [11018649](https://open.wenmarpro.com/bulletins/11018649), 2025-05-29: Module, Urea Pump/Level: HD 6.7L \(ETL/ETN/ETM\) with Mil On P21C4\-00 \(Reductant Line Heater Relay Control Circuit High / U11C1\-00 \(Reductant Control Module Received Implausible Data From ECM/PCM\), do not replace the DEF Pump. Follow TSB's released and appropriate Service Diagnostics.
- [11016060](https://open.wenmarpro.com/bulletins/11016060), 2025-03-28: "6 CONTROL UNIT, Diesel Exhaust Customer complaints with malfunction light illuminated on 2019 thru 2024 MY DJ / D2 / DD / DP vehicles with 6.7L \(ETL / ETM / ETN\) built on or before October 15,2024 and exhibiting DTCs P21C4\-00 \(Reductant Line Heater Relay Control Circuit High\) and / or U11C1\-00 \(Reductant Control Module received implausible Data from ECM / PCM\). These DTCs will occur after installation of service DCU 68458603AB. Do not replace parts until after the TSB 25\-008\-24 is performed. If the DTC\(s\) continue to set, then follow the Service Diagnostics for the applicable DTC."
- [11015599](https://open.wenmarpro.com/bulletins/11015599), 2025-03-13: Malfunction Indicator Lamp \(MIL\) Illumination, Diagnostic Trouble Codes \(DTCs\) P21C4 – \(Diesel Exhaust Fluid\) Reductant Line Heater Control Circuit High, and U11C1 – Reductant Control Module Received Implausible Data From ECM/PCM, Set
- [11010636](https://open.wenmarpro.com/bulletins/11010636), 2024-11-18: "Flash: Diesel Exhaust Fluid \(DEF\) Dosing Control Unit \(DCU\) Update Customers must experience a Malfunction Indicator Lamp \(MIL\) illumination and the vehicle must exhibit/set the following Diagnostic Trouble Code \(DTC\): ● P21C4\-00 \- Reductant Line Heater Relay Control Circuit High. ● U11C1\-00 \- Reductant Control Module Received Implausible Data From ECM/PCM. These DTCs will occur after installation of service DCU 68458603AB. This bulletin involves reprogramming the DCU with the latest available software."
- [10239975](https://open.wenmarpro.com/bulletins/10239975), 2023-07-31: Flash: Powertrain Control Module \(PCM\) Updates Customers may experience a Malfunction Indicator Lamp \(MIL\) illumination. Upon further investigation the technician may find that one or more of the following Diagnostic Trouble Codes \(DTC\)s have been set: ? \*\*P061B\-00 \- Internal Control Module Torque Calculation Performance. ? P0299\-00 \- Turbocharger Underboost.\*\* ? P0461\-00 \- Fuel Level Sensor 1 Performance. ? P0506 \- Idle Control System RPM \- Lower Than Expected. ? P20EE \- NOx Catalyst Efficiency Below Threshold. ? P1451\-00 \- Diesel Particulate Filter System Performance. ? P242F\-00 \- Diesel Particulate Filter Restriction \- Ash Accumulation. ? P2463\-00 \- Diesel Particulate Filter Restriction \- Soot Accumulation Bank 1. ? P026B \- Injection Timing Performance. ? P0607\-00 \- ECU Internal Performance. ? P20E8\-00 \- Reductant Pressure Too Low. ? P0301\-00 \- Cylinder 1 Misfire. ? P0302\-00 \- Cylinder 2 Misfire. ? P0303\-00 \- Cylinder 3 Misfire. ? P0304\-00 \- Cylinder 4 Misfire. ? P0305\-00 \- Cylinder 5 Misfire. ? P0306\-00 \- Cylinder 6 Misfire. ? P1C54\-00 \- SCR NOx Catalyst Missing. ? P2706\-00 \- MS Solenoid Circuit \(68RFE Only\). ? P1D73\-00 \- AGS Performance. ? P0421\-00 \- Catalyst 1 Efficiency Below Threshold Bank 1. ? P24A5\-00 \- EGR Cooler Bypass Bank 1 Control Stuck. ? P21C4\-00 \- Reductant Line Heater Relay Control Circuit High. ? P2560\-00 \- Engine Coolant Level Low. ? P2201\-00 \- Aftertreatment NOX Sensor Circuit Performance \- Bank 1 Sensor 1. ? P0604\-00 \- Internal Control Module Ram. ? P0607\-00 \- ECU Internal Performance. ? P0868\-00 \- Line Pressure Low \(Module, Powertrain Control \(PCM\), \(68RFE Only\). ? P0740\-00 \- TCC Out Of Range. ? P218F\-00 \- Reductant No Flow Detected. ? P226C \- Turbocharger Boost Control ?A? Slow Response \(In extreme cold ambient temperatures\). ? P061A \- Level 2 Torque Performance. ? P061E \- Internal Control Module Brake Signal Performance. ? P062C \- Etc Level 2 Mph Performance. ? P203F
- [10229550](https://open.wenmarpro.com/bulletins/10229550), 2023-01-09: Flash: Powertrain Control Module \(PCM\) Updates This bulletin involves reprogramming the Engine Control Module \(ECM\) / PowertrainControl Module \(PCM\) with the latest available software. Customers may experience a Malfunction Indicator Lamp \(MIL\) illumination. Upon further investigation the technician may find that one or moreof the following DTCs have been set: P0506 \- Idle Control System RPM \- Lower Than Expected. P0299\-00 \- Turbocharger Underboost. P20EE \- NOx Catalyst Efficiency Below Threshold. P1451\-00 \- Diesel Particulate Filter System Performance. P242F\-00 \- Diesel Particulate Filter Restriction \- Ash Accumulation. P2463\-00 \- Diesel Particulate Filter Restriction \- Soot Accumulation Bank 1. P026B \- Injection Timing Performance. P0607\-00 \- ECU Internal Performance. P20E8\-00 \- Reductant Pressure Too Low. P0301\-00 \- Cylinder 1 Misfire. P0302\-00 \- Cylinder 2 Misfire. P0303\-00 \- Cylinder 3 Misfire. P0304\-00 \- Cylinder 4 Misfire. P0305\-00 \- Cylinder 5 Misfire. P0306\-00 \- Cylinder 6 Misfire. P1C54\-00 \- SCR NOx Catalyst Missing. P2706\-00 \- MS Solenoid Circuit \(68RFE Only\). P1D73\-00 \- AGS Performance. P0421\-00 \- Catalyst 1 Efficiency Below Threshold Bank 1. P24A5\-00 \- EGR Cooler Bypass Bank 1 Control Stuck. P21C4\-00 \- Reductant Line Heater Relay Control Circuit High. P2560\-00 \- Engine Coolant Level Low. P2201\-00 \- Aftertreatment NOX Sensor Circuit Performance \- Bank 1 Sensor 1. P0604\-00 \- Internal Control Module Ram. P0607\-00 \- ECU Internal Performance. P0868\-00 \- Line Pressure Low \(Module, Powertrain Control \(PCM\),\(68RFE Only\). P0740\-00 \- TCC Out Of Range. P218F\-00 \- Reductant No Flow Detected. P226C \- Turbocharger Boost Control ?A? Slow Response \(In extreme cold ambienttemperatures\). P061A \- Level 2 Torque Performance. P061B \- Internal Control Module Torque Calculation Performance. P061E \- Internal Control Module Brake Signal Performance. P062C \- Etc Level 2 Mph Performance. P203F \- \(Diesel Exhaust Fluid\) Reductant Level Too Low. P0420 \- Catalyst System Efficien
- [10225402](https://open.wenmarpro.com/bulletins/10225402), 2022-10-31: Flash: Powertrain Control Module \(PCM\) Updates This bulletin involves reprogramming the Engine Control Module \(ECM\) / PowertrainControl Module \(PCM\) with the latest available software. Customers may experience a Malfunction Indicator Lamp \(MIL\) illumination. Upon further investigation the technician may find that one or moreof the following DTCs have been set: P0506 \- Idle Control System RPM \- Lower Than Expected. P0299\-00 \- Turbocharger Underboost. P20EE \- NOx Catalyst Efficiency Below Threshold. P1451\-00 \- Diesel Particulate Filter System Performance. P242F\-00 \- Diesel Particulate Filter Restriction \- Ash Accumulation. P2463\-00 \- Diesel Particulate Filter Restriction \- Soot Accumulation Bank 1. P026B \- Injection Timing Performance. P0607\-00 \- ECU Internal Performance. P20E8\-00 \- Reductant Pressure Too Low. P0301\-00 \- Cylinder 1 Misfire. P0302\-00 \- Cylinder 2 Misfire. P0303\-00 \- Cylinder 3 Misfire. P0304\-00 \- Cylinder 4 Misfire. P0305\-00 \- Cylinder 5 Misfire. P0306\-00 \- Cylinder 6 Misfire. P1C54\-00 \- SCR NOx Catalyst Missing. P2706\-00 \- MS Solenoid Circuit \(68RFE Only\). P1D73\-00 \- AGS Performance. P0421\-00 \- Catalyst 1 Efficiency Below Threshold Bank 1. P24A5\-00 \- EGR Cooler Bypass Bank 1 Control Stuck. P21C4\-00 \- Reductant Line Heater Relay Control Circuit High. P2560\-00 \- Engine Coolant Level Low. P2201\-00 \- Aftertreatment NOX Sensor Circuit Performance \- Bank 1 Sensor 1. P0604\-00 \- Internal Control Module Ram. P0607\-00 \- ECU Internal Performance. P0868\-00 \- Line Pressure Low \(Module, Powertrain Control \(PCM\),\(68RFE Only\). P0740\-00 \- TCC Out Of Range. P218F\-00 \- Reductant No Flow Detected. P226C \- Turbocharger Boost Control ?A? Slow Response \(In extreme cold ambienttemperatures\). P061A \- Level 2 Torque Performance. P061B \- Internal Control Module Torque Calculation Performance. P061E \- Internal Control Module Brake Signal Performance. P062C \- Etc Level 2 Mph Performance. P203F \- \(Diesel Exhaust Fluid\) Reductant Level Too Low. P0420 \- Catalyst System Efficien
- [10225265](https://open.wenmarpro.com/bulletins/10225265), 2022-10-31: Flash: Powertrain Control Module \(PCM\) Updates This bulletin involves reprogramming the Engine Control Module \(ECM\) / PowertrainControl Module \(PCM\) with the latest available software. Customers may experience a Malfunction Indicator Lamp \(MIL\) illumination. Upon further investigation the technician may find that one or moreof the following DTCs have been set: P0506 \- Idle Control System RPM \- Lower Than Expected. P0299\-00 \- Turbocharger Underboost. P20EE \- NOx Catalyst Efficiency Below Threshold. P1451\-00 \- Diesel Particulate Filter System Performance. P242F\-00 \- Diesel Particulate Filter Restriction \- Ash Accumulation. P2463\-00 \- Diesel Particulate Filter Restriction \- Soot Accumulation Bank 1. P026B \- Injection Timing Performance. P0607\-00 \- ECU Internal Performance. P20E8\-00 \- Reductant Pressure Too Low. P0301\-00 \- Cylinder 1 Misfire. P0302\-00 \- Cylinder 2 Misfire. P0303\-00 \- Cylinder 3 Misfire. P0304\-00 \- Cylinder 4 Misfire. P0305\-00 \- Cylinder 5 Misfire. P0306\-00 \- Cylinder 6 Misfire. P1C54\-00 \- SCR NOx Catalyst Missing. P2706\-00 \- MS Solenoid Circuit \(68RFE Only\). P1D73\-00 \- AGS Performance. P0421\-00 \- Catalyst 1 Efficiency Below Threshold Bank 1. P24A5\-00 \- EGR Cooler Bypass Bank 1 Control Stuck. P21C4\-00 \- Reductant Line Heater Relay Control Circuit High. P2560\-00 \- Engine Coolant Level Low. P2201\-00 \- Aftertreatment NOX Sensor Circuit Performance \- Bank 1 Sensor 1. P0604\-00 \- Internal Control Module Ram. P0607\-00 \- ECU Internal Performance. P0868\-00 \- Line Pressure Low \(Module, Powertrain Control \(PCM\),\(68RFE Only\). P0740\-00 \- TCC Out Of Range. P218F\-00 \- Reductant No Flow Detected. P226C \- Turbocharger Boost Control ?A? Slow Response \(In extreme cold ambienttemperatures\). P061A \- Level 2 Torque Performance. P061B \- Internal Control Module Torque Calculation Performance. P061E \- Internal Control Module Brake Signal Performance. P062C \- Etc Level 2 Mph Performance. P203F \- \(Diesel Exhaust Fluid\) Reductant Level Too Low. P0420 \- Catalyst System Efficien
- [10221867](https://open.wenmarpro.com/bulletins/10221867), 2022-09-26: Flash: Powertrain Control Module \(PCM\) Updates This bulletin involves reprogramming the Engine Control Module \(ECM\) / Powertrain Control Module \(PCM\) with the latest available software. Customers may experience a Malfunction Indicator Lamp \(MIL\) illumination. Upon further investigation the technician may find that one or more of the following Diagnostic Trouble Codes \(DTCs\) have been set:P2463\-00 \- Diesel Particulate Filter Restriction \- Soot Accumulation Bank 1. P242F\-00 \- Diesel Particulate Filter Restriction \- Ash Accumulation. P1D73\-00 \- AGS Performance. P0299\-00 \- Turbocharger Underboost\(Additional Improvement for D2 ETM Only\). P1451\-00 \- Diesel Particulate Filter System Performance. P0421\-00 \- Catalyst 1 Efficiency Below Threshold Bank 1. P24A5\-00 \- EGR Cooler Bypass Bank 1 Control Stuck. P21C4\-00 \- Reductant Line Heater Relay Control Circuit High. P2560\-00 \- Engine Coolant Level Low. P2201\-00 \- Aftertreatment NOX Sensor Circuit Performance \- Bank 1 Sensor 1. P0604\-00 \- Internal Control Module Ram. P0607\-00 \- ECU Internal Performance. P0868\-00 \- Line Pressure Low \(Module, Powertrain Control \(PCM\), 68RFE\). P0740\-00 \- TCC Out Of Range. P218F\-00 \-Reductant No Flow Detected. P20EE \- NOx Catalyst Efficiency Below Threshold. P226C \- Turbocharger Boost Control ?A? Slow Response \(In extreme cold ambient temperatures\). P061A \- Level 2 Torque Performance. P061B \- Internal Control Module Torque Calculation Performance. P061E \- Internal Control Module Brake Signal Performance. P062C \- Etc Level 2 Mph Performance. P203F \- \(Diesel Exhaust Fluid\) Reductant Level Too Low. P20E8 \- \(Diesel Exhaust Fluid\) Reductant Pressure Too Low. P0420 \- Catalyst System Efficiency Bank 1. U02A3 \- Lost of Communication with PM Sensor. P1507 \- Crankcase Filter Restriction. P0116 \- Engine Coolant Temperature Sensor Performance. P0106 \- Manifold Absolute Pressure Sensor Performance \(In extreme cold ambient temperatures\). U3017 \- Control Module Timer/Clock Performance.
- [10221348](https://open.wenmarpro.com/bulletins/10221348), 2022-09-26: Flash: Powertrain Control Module \(PCM\) Updates This bulletin involves reprogramming the Engine Control Module \(ECM\) / Powertrain Control Module \(PCM\) with the latest available software. Customers may experience a Malfunction Indicator Lamp \(MIL\) illumination. Upon further investigation the technician may find that one or more of the following Diagnostic Trouble Codes \(DTCs\) have been set: P0607\-00 \- ECU Internal Performance. P20E8\-00 \- Reductant Pressure Too Low. P0301\-00 \- Cylinder 1 Misfire\(Sym Cam Pump Only\). P0302\-00 \- Cylinder 2 Misfire\(Sym Cam Pump Only\). P0303\-00 \- Cylinder 3 Misfire\(Sym Cam Pump Only\). P0304\-00 \- Cylinder 4 Misfire\(Sym Cam Pump Only\). P0305\-00 \- Cylinder 5 Misfire\(Sym Cam Pump Only\). P0306\-00 \- Cylinder 6 Misfire\(Sym Cam Pump Only\). P1C54\-00 \- SCR NOx Catalyst Missing. P242F\-00 \- Diesel Particulate Filter Restriction \- Ash Accumulation\(68RFE Only\). P2463\-00 \- Diesel Particulate Filter Restriction \- Soot Accumulation Bank 1\(68RFE Only\). P1451\-00 \- Diesel Particulate Filter System Performance\(68RFE Only\). P0299\-00 \- Turbocharger Underboost. P2706\-00 \- MS Solenoid Circuit \(68RFE Only\). P2463\-00 \- Diesel Particulate Filter Restriction \- Soot Accumulation Bank 1. P242F\-00 \- Diesel Particulate Filter Restriction \- Ash Accumulation . P1D73\-00 \- AGS Performance. P0299\-00 \- Turbocharger Underboost\(Additional Improvement for D2 ETM Only\). P1451\-00 \- Diesel Particulate Filter System Performance. P0421\-00 \- Catalyst 1 Efficiency Below Threshold Bank 1. P24A5\-00 \- EGR Cooler Bypass Bank 1 Control Stuck. P21C4\-00 \- Reductant Line Heater Relay Control Circuit High. P2560\-00 \- Engine Coolant Level Low. P2201\-00 \- Aftertreatment NOX Sensor Circuit Performance \- Bank 1 Sensor 1. P0604\-00 \- Internal Control Module Ram. P0607\-00 \- ECU Internal Performance. P0868\-00 \- Line Pressure Low \(Module, Powertrain Control \(PCM\),\(68RFE Only\). P0740\-00 \- TCC Out Of Range. P218F\-00 \- Reductant No Flow Detected. P20EE \- NOx Catalyst Efficiency Below Threshold.