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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 94 (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

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.
  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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