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Home >> Chevrolet >> 2018 >> Equinox L >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 17 (Engine Controls And Fuel - 1.6L (LH7) Diesel - Diagnostic Information And Procedures (P205B - P2BAA) And Symptoms) >> Diagnostic Information And Procedures >> DTC P20EE, P249D, Or P249E: NOx Catalyst Efficiency Below Threshold/Closed Loop Reductant Injection Control At Limit - Flow Too Low/High >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition Off
  2. Test the reductant system for contamination. Refer to Contaminants-in-Diesel Exhaust Fluid Diagnosis .
    • If any conditions are found 

      Repair as necessary.

    • Go to next step: If no conditions are found 
  3. Ignition - On/Vehicle - In Service Mode
  4. Perform the scan tool control function: Reductant System Leak Test - ON
  5. Verify that the system is able to build up and reach the reductant pressure sensor parameter greater than 450 kPa.
    • If less than the specified range 
    1. Command the Reductant Pump to 50% with a scan tool.
    2. Verify the scan tool parameter: Desired Reductant Pump Speed = Reductant Pump Speed
      • If equal
    • Go to next step: If within the specified range 
  6. Verify there are no leaks, kinks or restrictions in the reductant lines
    • If any condition is found 

      Repair as necessary.

    • Go to next step: If no conditions are found 
  7. Verify the Reductant Injection Quantity Test  passes.
    • If the test does not pass 

      Repair as necessary.

    • Go to next step: If the test passes 
  8. Disconnect the Q61 Reductant Injector electrical connector.
  9. Engine running and NOx sensors at operating temperature, verify NOx sensor 2 NOx Concentration is less than 50 ppm greater than NOx sensor 1 NOx Concentration.
    • If NOx sensor 2 NOx Concentration is 50 ppm or greater than NOx sensor 1 NOx Concentration 

      Replace the B195B Nitrogen Oxides Sensor 2

    • Go to next step: If NOx sensor 2 NOx Concentration is less than 50 ppm greater than NOx sensor 1 NOx Concentration 
  10. Idle engine at 1, 500 RPM for 10 min while monitoring Exhaust Gas Temperature Sensor 2.
  11. Verify Exhaust Gas Temperature Sensor 2 is colder than 150°C (302°F)
    • If 150°C (302°F) or warmer 
    1. Verify Exhaust Gas Temperature Sensor 2 is warmer than 150°C (302°F) For greater than 30 min, then continue to the next step.
    • If colder than 150°C (302°F) 
  12. Verify NOx sensor 1 NOx Concentration and NOx sensor 2 NOx Concentration are within 50 ppm of each other.
    • If not within 50 ppm 

      Replace the B195A Nitrogen Oxides Sensor 1

    • Go to next step: If within 50 ppm 
  13. Connect the Q61 Reductant Injector electrical connector.
  14. Verify none of the conditions listed below exist:
    • If any condition is found 

      Repair as necessary

    • Go to next step: If no condition is found 
  15. Replace SCR Catalyst.
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