P11AF
DTC P0137, P0138, P11AF, P11B2, or P11B5
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 P0137
- HO2S Circuit Low Voltage Sensor 2
DTC P0138
- HO2S Circuit High Voltage Sensor 2
DTC P11AF
- HO2S Performance - Signal High During Moderate Load Sensor 2
DTC P11B2
- HO2S Performance - Signal Low During Moderate Load Sensor 2
DTC P11B5
- HO2S Current Performance Sensor 2
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
P0137 or P0138
* The engine speed is greater than 600 RPM.
* The battery voltage is greater than 11 V.
* The engine run time is greater than 10 s.
* The DTCs run continuously once the above conditions are met.
P11AF or P11B2
* The engine run time is greater than 10 s.
* The engine speed is between 1,300 and 2,600 RPM.
* The intake air temperature is between -43 to +123°C (-45 to +253°F).
* The BARO pressure is between 75-110 kPa (11-16 psi).
* The battery voltage is greater than 11 V.
* The EGR is commanded ON and the exhaust gas temperature sensor 2 is between 100-1,000°C (212-1,832° F).
* The DPF regeneration is not active.
* The fuel level is greater than 15 percent.
* The DTCs run continuously once the above conditions are met.
P11B5
* The engine speed is greater than 600 RPM.
* The battery voltage is greater than 11 V.
* The engine run time is greater than 10 s.
* The NOx sensor is at operating temperature.
* The DTC runs continuously once the above conditions are met.
Conditions for Setting the DTC
P0137 or P0138
The ECM receives a serial data message from the NOx sensor module that the time the diagnostic is enabled the HO2S signal is outside the normal limits for greater than 3 s.
P11AF or P11B2
The ECM receives a serial data message from the NOx sensor module that the HO2S signal is outside the normal limits during moderate engine load conditions for greater than 1 s.
P11B5
The NOx sensor module compares the HO2S diagnostic valid time to the HO2S invalid time. If the ratio is less than a calibrated threshold, this DTC sets.
Action Taken When the DTC Sets
DTCs P0137, P0138, P11AF, P11B2, and P11B5 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P0137, P0138, P11AF, P11B2, and P11B5 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. Verify the following conditions do not exist with the exhaust system:
* Leaks - Refer to Exhaust Leakage (Exhaust Leakage)
* Physical damage
* Loose or missing hardware
* Loose B195 NOx sensors or B131 exhaust temperature sensors
• If a condition is found, repair the exhaust system.
2. If the exhaust system tests normal, replace the B195 NOx sensor.
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.
Repair Instructions
* Nitrogen Oxide Sensor Replacement - Position 2 (Nitrogen Oxide Sensor Replacement - Position 2)
* Perform the scan tool NOx Sensor 2 Reset procedure after replacing the NOx sensor 2
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.