• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

The selective catalytic 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 reductant 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. The ECM varies the amount of reductant added by varying the reductant injector duty-cycle in response to changes in engine-out NOx levels.

The ECM supplies voltage to the reductant injector on the injector high control circuit. The ECM turns On the reductant injector by grounding the low control circuit of the injector.

It is common for reductant to crystallize over the nozzle of the reductant injector. The crystals will dissolve with use and the reductant injector will resume full functionality. The Reductant Quantity test may need to be performed multiple times to dissolve the crystallized reductant before diagnosing the reductant injector for performance issues.

Engine Controls Schematics

Master Electrical Component List

Exhaust Aftertreatment System Description

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

J–45873 Fuel Return Volume Test Kit

Warning: Diesel Exhaust Fluid (DEF) is corrosive. Do not allow it to come in contact with your skin, eyes, or the finished surfaces of the vehicle. If exposed, it may cause skin and eye irritation. Wear skin and eye protection when handling. Inhalation may cause irritation to the upper respiratory tract. Store in a cool, well-ventilated area. For more safety information, see the label of the Diesel Exhaust Fluid container. Failure to follow this procedure may result in injury and/or vehicle damage.

Note:

• Do not perform this diagnostic procedure unless you were sent here from another diagnostic procedure.
• Do not perform the Reductant Quantity Test if the diesel exhaust fluid (DEF) temperature is colder than −4°C (25°F).
• The Reductant Quantity Test may need to be run multiple times to dissolve crystallized reductant and to restore proper flow pattern.
• The NOx Catalyst Reductant-Load Adaptive Value can affect the quantity of reductant in the Reductant Injection Quantity Test. To reset this value and ensure the accuracy of the test, the scan tool NOx Catalyst Reductant Loading Reset must be performed prior to performing the test.
• Once the injector begins cycling, the Reductant Quantity Test takes approximately 5 minutes to run and the ECM will end the test after approximately 325 s.

1. Perform the scan tool NOx Catalyst Reductant Loading Reset.

Note: The gasket for the Q61 Emission Reduction Fluid Injector must be replaced when the injector is removed from the exhaust pipe.

2. Remove the Q61 Emission Reduction Fluid Injector from the exhaust leaving the reductant line connected.
3. Position the Q61 Emission Reduction Fluid Injector nozzle towards one of the graduated scale container from the J-45873. Command the Reductant Injection Quantity Test ON with a scan tool. Observe the injector spray pattern. 3 individual streams and atomization or mist of reductant should be observed.
• If the function does not perform as specified

  Inspect the Q61 Emission Reduction Fluid Injector lines for damage, restrictions, or blockage.

• If a condition is found, repair as necessary
• If no condition is found, replace the Q61 Emission Reduction Fluid Injector
• If the function performs as specified
4. When the test completes, verify 23–30 ml of fluid has flowed.
• If not between 23–30 ml
1. Disconnect the Q61 Emission Reduction Fluid Injector from the supply line.
2. Position the Q61 Emission Reduction Fluid Injector supply line towards the graduated scale container.

Note: The Reductant Injection Quantity Test runs for approximately 5 minutes when turned on, and cannot be turned off with the scan tool. The step below is performed using the scan tool Reductant System Leak Test function.

3. Command the Reductant System Leak Test ON with a scan tool.
4. Command the Reductant System Leak Test Off when 40 ml has flowed.
5. Verify that 40 ml has flowed within 1 minute.
• If less than 40 ml
6. Inspect the Q61 Reductant Injector and supply line for damage, restrictions, or blockage.
• If a condition is found, repair or replace as necessary.
• If no condition is found, replace the A38 Reductant Pump and Sensor Assembly.
• If greater than 40 ml
7. Replace the Q61 Reductant Injector.
• If between 23–30 ml
5. Return to referring document.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• Reductant Fluid Injector Replacement
• Emission Reduction Fluid Supply Pump Module Replacement for reductant pump and sensor assembly replacement.