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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 >> Fuel Pump Electrical Circuit Diagnosis >> 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 OFF and all vehicle systems OFF, disconnect the KR23A Fuel Pump Relay. It may take up to 2 minutes for all vehicle systems to power down.
  2. Verify the fuel pump is OFF
    • If the fuel pump is ON 

      Repair the short to voltage on the fuel pump relay component control circuit.

    • Go to next step: If the fuel pump is OFF 
  3. Test for less than 10 Ω between the ground circuit terminal 85 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • Go to next step: If less than 10 Ω 
  4. Ignition ON.
  5. Verify a test lamp illuminates between the ignition circuit terminal 87 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    3. Disconnect the harness connector at the G12 fuel pump.
    4. Test for infinite resistance between the component control circuit terminal 30 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, test or replace the KR23A fuel pump relay.
    • Go to next step: If the test lamp illuminates 
  6. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the G12 fuel pump. It may take up to 2 minutes for all vehicle systems to power down.
  7. Test for less than 10 Ω between the G12 fuel pump ground circuit terminal 4 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • Go to next step: If less than 10 Ω 
  8. Connect the harness connector at the G12 fuel pump.
  9. Ignition ON, connect a 20 A fused jumper wire between the ignition circuit terminal 87 and the component control circuit terminal 30.
  10. Verify the G12 fuel pump is activated.
    • If the G12 fuel pump does not activate 
    1. Ignition OFF, disconnect the harness connector at the G12 fuel pump.
    2. Test for less than 2 Ω in the control circuit terminal 3 end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the G12 fuel pump.
    • Go to next step: If the G12 fuel pump activates 
  11. Test or replace the KR23A fuel pump relay.
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