P204F
DTC P204F, P20E8, or P20E9
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 P204F
-
Reductant System Performance
DTC P20E8
-
Reductant Pressure Too Low
DTC P20E9
-
Reductant Pressure Too High
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. Upstream and downstream NOx sensors provide the engine control module (ECM) with engine-out and tailpipe-out NOx levels. The ECM varies the amount of DEF added by varying the reductant injector duty cycle in response to changes in engine-out NOx levels.
The ECM supplies system voltage to the reductant pump motor. The ECM controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. The ECM supplies a ground to the low reference circuit. As the duty-cycle increases, the output of the reductant pump increases.
Conditions for Running the DTCs
P204F
* DTCs P204B, P204C, P204D, P208A, P208D, P20A0, P20A2, or P20A3, are not set.
* The engine speed is greater than 600 RPM.
* The battery voltage is greater than 11 V.
* The DEF must not be frozen.
* The engine run time is greater than 10 s.
* The EGT sensor 2 is greater than 170°C (338°F) for 1 s.
* The DTC runs continuously when the above conditions are met.
20E8
* The reductant pump module pressure is less than 400 kPa (58 psi) for more than 60 s.
* The ambient air temperature is greater than -30°C (-22°F).
* The DEF must not be frozen.
* The EGT sensor 2 is greater than 170°C (338°F) for 1 s.
* The DTC runs continuously when the above conditions are met.
20E9
* The reductant pump module pressure is greater than 650 kPa (94 psi) for more than 10 s or greater than 795 kPa (115 psi) for more than 1 s.
* The ambient air temperature is greater than -30°C (-22°F).
* The EGT sensor 2 is greater than 170°C (338°F) for 1 s.
* The DEF must not be frozen.
* The DTC runs continuously when the above conditions are met.
Conditions for Setting the DTC
* The ECM detects the reductant pressure did not reach a calibrated threshold after an initial attempt to build up pressure. The ECM will then reduce reductant pressure and then attempt to build pressure two additional times. If the ECM detects reductant pressure is still less than a calibrated threshold, a DTC is set and the DEF telltale will set and the "Service Exhaust Fluid System - See Owner's Manual Now" will be displayed on the DIC.
Or
* The ECM detects the reductant pressure is greater than a calibrated threshold or less than a calibrated threshold.
Or
* The ECM detects the reductant pressure is greater than a calibrated value.
Action Taken When the DTC Sets
DTCs P204F, P20E8 and P20E9 are Type A DTCs.
The ECM inhibits the reductant system.
Conditions for Clearing the DTC
DTCs P204F, P20E8 and P20E9 are Type A DTCs.
Diagnostic Aids
A leak in the reductant system can be determined by inspecting for a build-up of crystallized diesel exhaust fluid (DEF).
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
Note:
Diesel exhaust fluid (DEF) that is frozen could cause these DTCs to set.
1. Using the Scan Tool, verify that the fluid level is showing at least 33 %. If less than 33 %, add DEF.
2. Ignition ON, observe the DTC information with a scan tool. DTC P1043, P1044, P1045, P1046, P1048, P1049, P202E, P2047, P2048, P204B, P204C, P204D, P208A, P208B, P208C, P208D, P20A1, P20A2, or P20A3 should not be set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
3. Ignition ON, command the Reductant System Leak Test ON with a scan tool. The reductant pump should turn ON.
• If the pump does not turn ON, refer to DTC P1043, P1044, P208A, P208C, or P208D P1043.
Note:
The diesel exhaust fluid (DEF) must be thawed before proceeding with this procedure.
4. 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).
5. 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. Test the diesel exhaust fluid for contamination. Refer to Contaminants-in-Diesel Exhaust Fluid Diagnosis Contaminants-in-Diesel Exhaust Fluid Diagnosis.
• If the diesel exhaust fluid is contaminated, replace the diesel exhaust fluid.
2. Ignition ON, command the Reductant System Leak Test ON with a scan tool. Allow the pressure to build for 2 minutes. Verify there are no leaks in the reductant lines.
• If a condition is found, repair as necessary.
3. Remove the Q61 emission reduction fluid injector from the exhaust pipe leaving the reductant line and electrical connector connected. Place the Q61 emission reduction fluid injector into a suitable container.
4. Ignition ON, command the Reductant System Leak Test ON with a scan tool. Allow the pressure to build. The Q61 emission reduction fluid injector should not leak.
• If a condition is found, replace the Q61 emission reduction fluid injector.
Note:
The diesel exhaust fluid (DEF) temperature 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. Observe the scan tool Reductant Pressure sensor parameter. The reading should be greater than 400 kPa (58 psi).
• If unable to build pressure, replace the G33 reductant tank assembly.
6. Perform the Emission Reduction Fluid Injector Quantity Test Emission Reduction Fluid Injector Quantity Test. The Q61 emission reduction fluid injector should pass the test.
• If the injector fails the test, replace the Q61 emission reduction fluid injector.
7. Verify the following conditions do not exist with the DEF system:
* Missing, restricted, or leaking reductant components
* Restricted or plugged reductant lines
* A skewed or shifted reductant pressure sensor.
* Restricted or plugged Q62 reductant purge valve, stuck closed
* High resistance in the G33 reductant pump motor or Q62 reductant purge valve circuits
* Inspect the harness connectors and the ground circuits of the DEF tank for poor connections.
• If a condition is found, repair as necessary.
8. If all components test normal, replace the G33 reductant tank assembly.
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.
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) temperature 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. 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.