P204C
DTC P204C or P204D
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P204C
-
Reductant Pressure Sensor Circuit Low Voltage
DTC P204D
-
Reductant Pressure Sensor Circuit High Voltage
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The selective catalytic reduction (SCR) system reduces oxides of nitrogen (NOx) emissions by injecting a metered amount of diesel exhaust fluid (DEF) or reductant into the exhaust gas stream entering the SCR catalyst. Within the SCR catalyst, the DEF reacts with the NOx to form nitrogen, carbon dioxide, and water vapor.
The engine control module (ECM) uses the reductant pressure sensor to maintain a desired reductant pump pressure. The engine control module (ECM) supplies 5 V on the 5 V reference circuit and ground on the low reference circuit. The ECM receives a varying signal voltage on the signal circuit. The ECM monitors the voltage on the reductant pressure sensor signal circuit.
Conditions for Running the DTC
* The engine speed is greater than 600 RPM.
* The battery voltage is greater than 11 V.
* The DTCs run continuously when the above condition is met.
Conditions for Setting the DTC
P204C
The ECM detects that the reductant pressure sensor signal is less than 0.41 V for greater than 0.4 s.
P204D
The ECM detects that the reductant pressure sensor signal is greater than 4.8 V for greater than 0.4 s.
Action Taken When the DTC Sets
DTC P204C and P204D are Type A DTCs.
The ECM inhibits the reductant system when DTC P204D is set.
Conditions for Clearing the DTC
DTC P204C and P204D are Type A DTCs.
Diagnostic Aids
If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the scan tool parameters for the component. The scan tool parameters will change abruptly if there is a condition with the circuit or a connection.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
* Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Quality) Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Quality)Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Level) Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Level)Diesel Exhaust Fluid (DEF) Warning Strategy (Emission Control) Diesel Exhaust Fluid (DEF) Warning Strategy (Emission Control)Diesel Exhaust Fluid (DEF) Warning Strategy (Anti-Tampering) Diesel Exhaust Fluid (DEF) Warning Strategy (Anti-Tampering)
* Exhaust Aftertreatment System Description Emission Control Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. DTC P06D2 should not be set.
• If a DTC is set, refer to DTC P0641, P0651, P0697, P06A3, P06D2, or P06D6 P0641 for further diagnosis.
2. Ignition ON, command the Reductant System Leak Test ON with a scan tool. Allow the pressure to build for at least 2 minutes. The first 60 s, the system performs a system purge. Observe the scan tool Reductant Pressure sensor parameter. The reading should be between 400-650 kPa (58-94 psi) and there should be no leaks in the system.
3. Ignition ON, observe the DTC information with a scan tool. DTC P204C or P204D should not be set.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, disconnect the 24-way harness connector at the DEF Tank. Refer to Inline Harness Connector End Views X100 for connector identification.
Note:
Testing for steps 2-4 is performed on the ECM side of the harness connector.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohms between the low reference circuit terminal C8 and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.
3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal A8 and ground.
• If less than the specified range, test the 5 V reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K20 ECM.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
4. Verify the scan tool reductant pressure sensor parameter is 0 kPa.
• If greater than the specified value, test the signal circuit terminal B8 for a short to voltage. If the circuit tests normal, replace the K20 ECM.
5. Install a 3 A fused jumper wire between the signal circuit terminal B8 and the 5 V reference circuit terminal A8. Verify the scan tool reductant pressure sensor parameter should be greater than 700 kPa (102 psi).
• If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
Note:
Testing for this step is performed on the DEF tank side of the harness connector.
6. Remove the DEF tank and test, inspect, and repair the items listed below. If all items test normal, replace the B194 emission reduction fluid tank pressure sensor.
* Poor connection at the 24-way harness connector
* Open or shorted DEF 5 V reference circuit
* Open or shorted DEF pressure sensor signal circuit
* Open DEF low reference circuit
Repair Instructions
* Emission Reduction Fluid Tank Replacement Emission Reduction Fluid Tank Replacement
* Perform the scan tool Reductant System Reset procedure after replacing the emission reduction fluid tank.
* Control Module References Control Module References for engine control module replacement, programming, and setup
Repair Verification
1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes.
Note:
The diesel exhaust fluid (DEF) and ambient air temperatures must be greater than -7°C (19°F) before proceeding with this procedure.
5. Ignition ON, command the Reductant System Leak Test ON with a scan tool. Allow the pressure to build for at least 2 minutes. The first 60 s, the system performs a system purge. Observe the scan tool Reductant Pressure sensor parameter. The reading should be between 400-650 kPa (58-94 psi) and there should be no leaks in the system.
6. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes.
7. Engine idling for 30 s.
8. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes.
9. Ignition ON, perform the Reductant System Data Reset with a scan tool in order to clear the DEF lamp.
• If the DEF lamp does not turn OFF, a condition with the system still exists.