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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 ambient air temperature is greater than -30°C (-22°F).

* The exhaust gas 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 A DTC.

* The ECM inhibits the reductant system.

Conditions for Clearing the DTC

DTC P204B is a Type A DTC.

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 Exhaust Aftertreatment System Description

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.

2. Observe the scan tool Reductant Pressure. The reading should be 0 kPa.

• If greater than 0 kPa
Refer to Circuit/System Testing

• If 0 kPa

3. Verify DTC P06D2 is not set.

• If the DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle

• If the DTC is not set

4. 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

• If within the specified range

5. 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 0 kPa
Refer to DTC P20A1 P20A1

• If 0 kPa

6. Observe the DTC information with a scan tool. DTC P204B should not set.

• If the DTC is set
Refer to Circuit/System Testing

• If the DTC is not set

7. 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.

8. Verify a DTC does not set.

• If any DTC sets
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

• If no DTC sets

9. All OK.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect 24-way harness connector at the DEF tank. It may take up to 2 minutes for all vehicle systems to power down.

Note: Testing for steps 2-5 is performed on the ECM side of the harness connector.

2. Test for less than 5 ohms between the low reference circuit terminal C8 and ground.

• If greater than 5 ohms

1. Disconnect the harness connector at the K20 Engine Control Module.

2. Test for less than 2 ohms in the low reference circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K20 Engine Control Module.

• If less than 5 ohms

3. Ignition ON.

4. Test for 4.8-5.2 V between the 5 V reference circuit terminal A8 and ground.

• If less than 4.8 V

1. Test for infinite resistance between the 5 V reference circuit and ground.

• If less than infinite resistance, repair the short to ground in the circuit.

• If infinite resistance

2. Test for less than 2 ohms in the 5 V reference circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K20 Engine Control Module.

• If greater than 5.2 V

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.

2. Ignition ON.

3. Test for less than 1 V between the 5 V reference circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K20 Engine Control Module.

• If between 4.8-5.2 V

5. Verify the scan tool reductant pressure sensor parameter is 0 kPa.

• If greater than the specified value

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.

2. Ignition ON.

3. Test for less than 1 V between the signal circuit terminal B8 and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K20 Engine Control Module.

• If equal to the specified value

6. Install a 3 A fused jumper wire between the signal circuit terminal B8 and the 5 V reference circuit terminal A8.

7. Verify the scan tool reductant pressure sensor parameter should be greater than 700 kPa (102 psi).

• If less than the specified value

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.

2. Test for infinite resistance between the signal circuit terminal and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the signal circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K20 Engine Control Module.

• If greater than the specified value

Note: Testing for this step is performed on the DEF tank side of the harness connector.

8. 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

* 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

• If a condition is found
Repair as necessary

• If no condition is found

9. Replace the emission reduction fluid 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.

* 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.

* Exhaust Gas Temperature (EGT) sensor 2 must be less than 200°C (392°F) prior to running the Reductant System Leak Test.

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.

• If the DEF lamp turns OFF

10. Perform the Reductant System Malfunction Warning Test Component Tests and General Diagnostics with a scan tool in order to clear the Service Emission System message, if illuminated.

• If the Service Emission System message does not turn OFF
A condition with the system still exists

• If the Service Emission System message turns OFF

11. All OK.

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