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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 54 (Engine Controls And Fuel - 2.8L (LWN) Diesel - Diagnostic Information And Procedures (2 Of 3)) >> Diagnostic Information and Procedures >> DTC P16D7-P16D9 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Remove the component: KR121A Reductant Control Module Relay 1 & KR121B Reductant Control Module Relay 2
  3. Test for less than 10 ohms between the test points:
    • KR121A Reductant Control Module Relay 1 - Ground circuit terminal 86/4 & Ground
    • KR121B Reductant Control Module Relay 2 - Ground circuit terminal 86/22 & Ground
    • If 10 ohms or greater 
    1. Disconnect the ground connection: G117
    2. Test for less than 2 ohms between the test points:
      • KR121A Reductant Control Module Relay 1 - Ground circuit terminal 86/4 & Terminal G117
      • KR121B Reductant Control Module Relay 2 - Ground circuit terminal 86/22 & Terminal G117
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Repair the open/high resistance in the ground connection.
    • Go to next step: If less than 10 ohms 
  4. Connect a DMM, set on the diode setting, between the test points:
    • Red lead @ B+ & Black lead @ KR121A Reductant Control Module Relay 1 - Control circuit terminal 85/6
    • Red lead @ B+ & Black lead @ KR121B Reductant Control Module Relay 2 - Control circuit terminal 85/20
  5. Ignition - On / Vehicle - In Service Mode
  6. Perform the scan tool control function: Sensor Supply Voltage Relay - Off

    Verify the DMM displays greater than 2. 5 V or displays O. L.

    • If 2. 5 V or less 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector : X1 @ K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points:
      • KR121A Reductant Control Module Relay 1 - Control circuit terminal 85/6 @ Relay Socket & Ground
      • KR121B Reductant Control Module Relay 2 - Control circuit terminal 85/20 @ Relay Socket & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for infinite resistance between the test points:
      • KR121A Reductant Control Module Relay 1 - Control circuit terminal 85/6 @ Relay Socket & Ground
      • KR121B Reductant Control Module Relay 2 - Control circuit terminal 85/20 @ Relay Socket & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component: K20 Engine Control Module
    • Go to next step: If greater than 2. 5 V or displays O. L. 
  7. Connect a DMM, set on the diode setting, between the test points:
    • KR121A Reductant Control Module Relay 1 - Control circuit terminal 85/6 @ Relay Socket & Ground
    • KR121B Reductant Control Module Relay 2 - Control circuit terminal 85/20 @ Relay Socket & Ground
  8. Perform the scan tool control function: Sensor Supply Voltage Relay - On

    Verify the DMM displays less than 1 V.

    • If 1 V or greater or displays O. L. 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector : X1 @ K20 Engine Control Module
    3. Test for less than 2 ohms between the test points:
      • KR121A Reductant Control Module Relay 1 - Control circuit terminal 85/6 @ Relay Socket & Terminal 65 @ Control module harness
      • KR121B Reductant Control Module Relay 2 - Control circuit terminal 85/20 @ Relay Socket & Terminal 65 @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K20 Engine Control Module
    • Go to next step: If less than 1 V 
  9. Test or replace the component: KR121A Reductant Control Module Relay 1 or KR121B Reductant Control Module Relay 2
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