P204B
DTC P204B
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 P204B
- Reductant Pressure Sensor Performance
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The reductant pressure sensor responds to pressure changes in the reductant system. The engine control module (ECM) supplies 5 V to the reductant pressure sensor on the 5 V reference circuit and provides a ground on the low reference circuit. The reductant pressure sensor provides a signal to the ECM on the sensor signal circuit which is relative to the pressure changes in the reductant system.
Condition for Running the DTC
* DTCs P204C or P204D are not set.
* The ignition is ON.
* The BARO pressure is greater than 75 kPa (11 psi).
* The ambient air temperatures is warmer than -7°C (19°F).
* The exhaust temperature sensor 2 is less than 170°C (338° F).
* The DTC runs continuously when the above conditions are met.
Conditions for Setting the DTC
The ECM detects the difference between the reductant pressure and the BARO pressure is greater than 50 kPa for greater than 1 s.
Action Taken When the DTC Sets
DTC P204B is a Type B DTC.
The ECM inhibits the reductant system.
Conditions for Clearing the DTC
DTC P204B is a Type B DTC.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
* Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Level) (Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Level)) Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Quality) (Diesel Exhaust Fluid (DEF) Warning Strategy (DEF Quality)) 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 (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Observe the scan tool Reductant Pressure when turning the ignition ON. The reading should be 0 kPa.
• If greater than the specified value, refer to DTC P20A1 (P20A1) for further diagnosis.
2. Ignition ON, compare the scan tool BARO pressure sensor parameter to the reading in the Altitude Versus Barometric Pressure (Altitude Versus Barometric Pressure) table. The reading should be within the specified range indicated in the table.
• If not within the specified range, refer to DTC P0106 (P0106) for further diagnosis.
3. Observe the DTC information with a scan tool. DTC P06D2 should not set.
• If a DTC is set, refer to DTC P0641, P0651, P0697, P06A3, P06D2, or P06D6 (P0641) for further diagnosis.
4. Observe the DTC information with a scan tool. DTC P204B should not set.
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. Ignition OFF, disconnect the 24-way harness connector at the DEF Tank. Refer to Inline Harness Connector End Views (Connector End Views By Number) 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 ohm 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 is 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 reductant pressure sensor.
* Restricted reductant components
* Restricted or plugged reductant lines
* Restricted or plugged Q62 reductant purge valve - Stuck closed
* A skewed or shifted reductant pressure sensor.
* High resistance in the Q62 reductant pressure sensor circuits
* 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 (Programming and Relearning) 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 30 s. Observe the scan tool Reductant Pressure sensor parameter. The reading should be between 425-575 kPa and there should be no leaks in the system.
Warning
Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
6. Engine idling at operating temperature. Accelerate at part throttle to 32-48 km/h (20-30 mph) for up to 5 minutes or until the DEF lamp turns OFF. The DEF lamp should turn OFF.
• If the DEF lamp does not turn OFF, a condition with the system still exists.