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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 278 (Engine Controls And Fuel - 3.6L (LGX LF4) - DTC P0117 (LGX) To DTC P0697) >> Diagnostic Information and Procedures >> DTC P0627-P0629: Fuel Pump Speed (LGX) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, all vehicle system OFF, disconnect the harness connector at the K38 Chassis Control Module. It may take up to 2 min for all vehicle systems to power down.
  2. Ignition ON.
  3. Test for less than 1 V between the K38 Chassis Control Module enable circuit terminal 20 and ground.
    • If 1 V or greater 
    1. Disconnect the X1 harness connector at the K20 Engine Control Module.
    2. Test for less than 1 V between the K38 Chassis Control Module enable circuit terminal 20 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, test or replace the K20 Engine Control Module.
    • If less than 1 V 
  4. Ignition OFF, Install a test lamp between the fuel pump speed output circuit at the K38 Chassis Control Module connector terminal 20 and ground.
  5. Ignition ON.
  6. Command the Fuel Pump Speed Increase with a scan tool.
  7. Verify the test lamp illuminates.
    • If the test lamp does not illuminate 
    1. Disconnect the X1 harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the K38 Chassis Control Module fuel pump speed output circuit terminal 20 and ground.
      • If less than infinite, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω on the K38 Chassis Control Module fuel pump speed output circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, test or replace the K20 Engine Control Module.
    • If the test lamp illuminates 
  8. Test or replace the K38 Chassis Control Module.
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