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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 12 (Engine Controls And Fuel - 2.8L (LWN) Diesel - Diagnostic Information And Procedures (3 Of 3)) >> Diagnostic Information and Procedures >> DTC P2687-P2689 >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition/Vehicle & All vehicle systems - Off
  2. Remove the component : KR22 Fuel Heater Relay
  3. Ignition - On / Vehicle - In Service Mode
  4. Verify a test lamp turns On between the test points : Ignition circuit terminal 85 & Ground
    • If the test lamp does not turn On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Remove the component : KR75 Engine Controls Ignition Relay
    3. Test for less than 2 ohms between the test points : Ignition circuit terminal 85 @ KR22 Fuel Heater Relay - Relay Socket & Control circuit terminal 87 @ KR75 Engine Controls Ignition Relay - Relay Socket
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Verify the fuse is OK and there is voltage at the fuse.
    • Go to next step : If the test lamp turns On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Test for infinite resistance between the test points : Ignition circuit terminal 85 & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component : KR22 Fuel Heater Relay
    • Go to next step : If the test lamp turns On 
  5. Verify a test lamp does not turn On between the test points : Control circuit terminal 86 & B+
    • If the test lamp turns On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector : X3 @ K20 Engine Control Module
    3. Test for infinite resistance between the test points : Control circuit terminal 86 @ 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 the test lamp does not turn On 
  6. Remove - Test Lamp
  7. Perform the scan tool control function : Fuel Heater Relay - On

    Verify the scan tool parameter : Fuel Heater Relay Control Circuit High Voltage Test Status = OK

    • If not the specified state 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector : X3 @ K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points : Control circuit terminal 86 @ Relay Socket & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component : K20 Engine Control Module
    • Go to next step : If the specified state 
  8. Connect a 3 A fused jumper wire between the test points : Control circuit terminal 86 & Ignition circuit terminal 85
  9. Perform the scan tool control function : Fuel Heater Relay - On

    Verify the scan tool parameter : Fuel Heater Relay Control Circuit High Voltage Test Status = Malfunction

    • If not the specified state 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the electrical connector : X3 @ K20 Engine Control Module
    3. Test for less than 2 ohms between the test points : Control circuit terminal 86 @ Relay Socket & Terminal 45 @ 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 the specified state 
  10. Verify a test lamp turns On between the test points : Ignition circuit terminal 87 & Ground
    • If the test lamp does not turn On and the circuit fuse is OK 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Test for less than 2 ohms between the test points : Ignition circuit terminal 87 @ Relay Socket & Output terminal @ X50A Fuse Block - Underhood F44UA Fuse
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Verify the fuse is OK and there is voltage at the fuse.
    • If the test lamp does not turn On and the circuit fuse is open 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Test for infinite resistance between the test points : Ignition circuit terminal 87 & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step : If infinite resistance
    3. Disconnect the electrical connector : K20 Engine Control Module
    4. Test for infinite resistance between the test points : Control circuit terminal 30 @ Relay Socket & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step : If infinite resistance
    5. Replace the component : E11A Fuel Heater/Water in Fuel Sensor F44UA Fuse
    6. Install the component : KR22 Fuel Heater Relay
    7. Connect a test lamp between the test points : Control circuit terminal 4 & Ground circuit terminal 3
    8. Ignition - On / Vehicle - In Service Mode
    9. Perform the scan tool control function : Fuel Heater Relay - On and Off

      Verify the test lamp turns On and Off.

      • If the test lamp does not turn On and Off - Test or replace the component : KR22 Fuel Heater Relay
      • If the test lamp turns On and Off - Test or replace the component : E11A Fuel Heater/Water in Fuel Sensor
    • Go to next step : If the test lamp turns On 
  11. Ignition/Vehicle & All vehicle systems - Off
  12. Install the component : KR22 Fuel Heater Relay
  13. Disconnect the electrical connector : E11A Fuel Heater/Water in Fuel Sensor
  14. Test for less than 10 ohms between the test points : Ground circuit terminal 3 & Ground
    • If 10 ohms or greater 
    1. Disconnect the ground connection : G404
    2. Test for less than 2 ohms between the test points : Ground circuit terminal 3 @ Component harness & Terminal G404
      • 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 
  15. Connect a test lamp between the test points : Control circuit terminal 4 & Ground circuit terminal 3
  16. Ignition - On / Vehicle - In Service Mode
  17. Perform the scan tool control function : Fuel Heater Relay - On and Off

    Verify the test lamp turns On and Off.

    • If the test lamp is always Off 

      Repair the open/high resistance in the circuit : Control Circuit

    • If the test lamp is always On 

      Repair the short to voltage on the circuit : Control Circuit

    • Go to next step : If the test lamp turns On and Off 
  18. Test or replace the component : E11A Fuel Heater/Water in Fuel Sensor
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