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P20C0




DTC P20B9, P20BA-P20BF, or P20C0-P20C4

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 P20B9
- Reductant Heater 1 Control Circuit

DTC P20BA
- Reductant Heater 1 Performance

DTC P20BB
- Reductant Heater 1 Control Circuit Low Voltage

DTC P20BC
- Reductant Heater 1 Control Circuit High Voltage

DTC P20BD
- Reductant Heater 2 Control Circuit

DTC P20BF
- Reductant Heater 2 Control Circuit Low Voltage

DTC P20C0
- Reductant Heater 2 Control Circuit High Voltage

DTC P20C1
- Reductant Heater 3 Control Circuit

DTC P20C3
- Reductant Heater 3 Control Circuit Low Voltage

DTC P20C4
- Reductant Heater 3 Control Circuit High Voltage

Diagnostic Fault Information






Circuit/System Description

The selective catalyst 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 in parts per million (ppm). The ECM then adjusts the amount of DEF injected upstream of the SCR based on the NOx concentration. Engine-out NOx levels as measured by NOx Sensor 1 will either increase (high ppm) or decrease (low ppm) the amount of DEF injected. The NOx concentration as measured by NOx Sensor 2 provides the ECM with both an indication of the NOx conversion efficiency within the SCR as well as confirming proper operation of the DEF system.

Conditions for Running the DTCs

P20B9, P20BD, or P20C1
* DTC P220B is not set.
* The DEF heater is commanded ON.
* The glow plug control module temperature is less than 123°C (254°F).
* The glow plug control module battery voltage is between 7-16 V.
* The DTCs run continuously once the above conditions are met.

P20BA
* DTC P205B, P205C, and P205D are not set.
* The emission reduction fluid tank heaters are active for 1,000-3,000 s.
* The emission reduction fluid tank level sensor reading is 100 %.
* The emission reduction fluid tank temperature is colder than -16°C (3°F).
* The vehicle speed is greater than 5 km/h (3 mph).
* The battery voltage is greater than 11 V.
* The engine speed is greater than 600 RPM.

P20BB, P20BF, or P20C3
* DTC P220B is not set.
* The DEF heater is commanded ON.
* The glow plug control module temperature is less than 123°C (254°F).
* The glow plug control module battery voltage is between 7-16.5 V.
* The DTCs run continuously once the above conditions are met.

P20BC, P20C0, or P20C4

The DEF heater is commanded OFF.

Conditions for Setting the DTC

P20B9, P20BD, or P20C1

The ECM receives a GPCM serial data message indicating the heater control circuit is open for greater than 3 s.

P20BA

The ECM receives a GPCM serial data message indicating the heater temperature difference between the start temperature and current temperature is less than a predetermined value.

P20BB, P20BF, or P20C3

The ECM receives a GPCM serial data message indicating the heater control circuit is shorted to ground or overloaded for greater than 1 s.

P20BC, P20C0, or P20C4

The ECM receives a GPCM serial data message indicating the heater control circuit is shorted to a voltage for greater than 2 s.

Action Taken When the DTC Sets

* DTCs P20B9, P20BB, P20BC, P20BD, P20BF, P20C0, P20C1, P20C3, and P20C4 are Type A DTCs.
* DTC P20BA is a Type B DTC.

Conditions for Clearing the DTC

* DTCs P20B9, P20BB, P20BC, P20BD, P20BF, P20C0, P20C1, P20C3, and P20C4 are Type A DTCs.
* DTC P20BA is a Type B 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 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)Diesel Exhaust Fluid (DEF) Warning Strategy (Emission Control) Diesel Exhaust Fluid (DEF) Warning Strategy (Emission Control)
* 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 scan tool GPCM control circuit status parameters listed below with a scan tool:

* Reductant Heater 1, 2, or 3 Ctrl Ckt Short Gnd Test Status
* Reductant Heater 1, 2, or 3 Ctrl Ckt Open Test Status
* Reductant Heater 1, 2, or 3 Ctrl Ckt Short Volts Test Status
Each parameter should display OK or Not Run

2. Command the GPCM Reductant Heater 1, 2, or 3 ON and OFF with a scan tool. Observe the scan tool GPCM Reductant Heater 1, 2, or 3 Current parameter. The reading should be between 5-7 Amps for heater 1, 0.75-2 Amps for heater 2, and 1.5-3 Amps for heater 3.
3. 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

Note: When testing the low reference circuits, verify all vehicle systems are completely OFF for at least 2 minutes. This includes retained accessory power (RAP) and the scan tool.

Refer to Testing Ground and Low Reference Circuits Testing Ground and Low Reference Circuits for further information on testing the low reference circuits.

1. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down, disconnect the X395 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 GPCM side of the harness connector.

2. Ignition OFF and all vehicle systems OFF, test for less than 5 ohm between the appropriate ground circuit listed below and ground.

* DEF heating tank (2) heater ground circuit terminal A4
* DEF pump line heater ground circuit terminal B4
* DEF reservoir heater ground circuit terminal C4

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, connect a test light between the appropriate control circuit listed below and ground. Command the GPCM Reductant Heater 1, 2, or 3 with a scan tool. The test lamp should illuminate.

* DEF heating tank (2) heater control circuit terminal A5
* DEF pump line heater control circuit terminal B5
* DEF reservoir heater control circuit terminal C5

• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the glow plug control module.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the glow plug control module.

Note:
* Testing for the remaining steps are performed on the DEF Tank side of the 24-way harness connector.
* Do not use the ground circuits in the 24-way harness connector.

4. Test for infinite resistance between each terminal listed below and ground.

* DEF heating tank (2) heater control circuit terminal A5
* DEF pump line heater control circuit terminal B5
* DEF reservoir heater control circuit terminal C5

• If not the specified value, test the control circuit for a short to ground or voltage. If the circuit tests normal, replace the reductant heater.

5. Measure the resistance between the control circuit and ground circuit terminals listed below. The reading should be between 2-4 ohm for the reductant reservoir heater 1, 8-10 ohm for the supply line heater 2, and 3-5 ohm for the reductant pump heater 3.

* DEF heating tank (2) heater control circuit terminal A5 and ground circuit terminal A4
* DEF pump line heater control circuit terminal B5 and ground circuit terminal B4
* DEF reservoir heater control circuit terminal C5 and ground circuit terminal C4

• If not within the specified range, test the heater control and ground circuits for an open. If the circuits test normal, replace the appropriate reductant heater.

Repair Instructions

* Emission Reduction Fluid Exhaust Front Pipe Injector Supply Pipe Replacement Service and Repair
* 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 glow plug 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. Observe the scan tool Reductant Pressure sensor parameter. The reading should be between 400-83 kPa 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.

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