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P220A




DTC P220A or P220B

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 P220A
- NOx Sensor 1 Supply Voltage Circuit

DTC P220B
- NOx Sensor 2 Supply Voltage Circuit

Diagnostic Fault Information





Circuit/System Description

The reductant system uses two nitrogen oxide (NOx) sensors to monitor the amount of NOx in the engine's exhaust gas. The first sensor is located at the outlet of the turbocharger and monitors the engine out NOx level. The second NOx sensor is located between the selective catalytic reduction (SCR) and the diesel particulate filter (DPF) and monitors NOx levels downstream of the SCR. The second NOx sensor also provides the engine control module (ECM) with information on the exhaust oxygen level during DPF regeneration.

Each NOx sensor contains a sensing cell, a pumping cell, and a heater. A sample of exhaust gas passes through a diffusion gap between the sensing cell and the pumping cell. The NOx sensor maintains a constant reference voltage across the sensing cell. An electronic circuit within sensor controls the pump current through the pumping cell in order to maintain a constant voltage in the sensing cell. The amount of current required to maintain the reference voltage in the sensing cell is proportional to the concentration of NOx in the exhaust.

The ECM varies the amount of diesel exhaust fluid (DEF) or reductant added by varying the reductant injector duty cycle in response to changes in engine exhaust out NOx levels.

The smart NOx sensors consist of two components, the NOx module and the NOx sensor element that are serviced as a unit. A circuit or performance condition with a NOx sensor is detected by the NOx sensor module. The smart NOx sensor module communicates the condition to the ECM over the serial data line. The ECM sets a DTC when a serial data message is received from the NOx sensor module.

Conditions for Running the DTCs

* The ignition is ON.
* The DTCs run continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM receives a serial data message from the GPCM indicating an internal controller circuit fault for greater than 3 s.

Action Taken When the DTC Sets

DTCs P220A and P220B are Type B DTCs.

Conditions for Clearing the DTC

DTCs P220A and P220B are Type B DTCs.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
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 ON, clear the DTC information with a scan tool. Ignition OFF for 2 minutes.
2. Engine idling, observe the DTC information with a scan tool. DTC P220A or P220B should not set.
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

1. Ignition OFF, disconnect the harness connector at the appropriate B195 NOx sensor.
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 4 and ground.

• If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the GPCM.

3. Ignition OFF, connect a test lamp between the ignition voltage circuit terminal 1 and ground. The test lamp should not illuminate.

• If the test lamp illuminates, test the ignition voltage circuit for a short to voltage. If the circuit tests normal, replace the GPCM.

4. Ignition ON for 10 s, the test lamp should illuminate.

• If the test lamp does not illuminates, test the ignition voltage circuit terminal 1 for a short to ground or an open/high resistance. If the circuit tests normal, replace the GPCM.

5. If all circuits test normal, replace the GPCM.

Repair Instructions

Control Module References (Programming and Relearning) for glow plug control module (GPCM) 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.

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.

5. 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.

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