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HOMESERVICE MANUALSCHEVROLET2019EXPRESS 2500 BASE, VAN CARGO EXTENDED, 6.0L ENG VIN GREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 13 (ENGINE CONTROLS AND FUEL - 2.8L (LWN) DIESEL - DIAGNOSTIC INFORMATION AND PROCEDURES (2 OF 3))DIAGNOSTIC INFORMATION AND PROCEDURESDTC P16D7-P16D9CIRCUIT/SYSTEM TESTING
2019 Chevrolet Express 2500 Base, Van Cargo Extended, 6.0L Eng VIN G

Circuit/System Testing

2019 Chevrolet Express 2500 Base, Van Cargo Extended, 6.0L Eng VIN GSECTION Circuit/System Testing
WARNING: This page is about a different variant/trim than selected.
    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
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.