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HOMESERVICE MANUALSCHEVROLET2025TRAILBLAZER ACTIV, FWDREPAIR AND DIAGNOSIS (SINGLE PAGE)BODY & FRAMEBODY, CAB CONTROL SYSTEMSSECONDARY AND CONFIGURABLE CUSTOMER CONTROLSDIAGNOSTIC INFORMATION AND PROCEDURESDRIVE MODE SWITCH MALFUNCTIONCIRCUIT/SYSTEM TESTING
2025 Chevrolet Trailblazer ACTIV, FWD

Circuit/System Testing

2025 Chevrolet Trailblazer ACTIV, FWDSECTION Circuit/System Testing
  1. Ignition/Vehicle OFF and all vehicle systems OFF. It may take up to 2 min for all vehicle systems to power down.
  2. Disconnect the harness connector at the S48E Multifunction Switch - Center Console.
  3. Verify a test lamp illuminates between Ground circuit terminal 3 and B+.
    • If the test lamp does not illuminate 

      Repair the open or high resistance on circuit 350 or the ground point for circuit 350.

    • Go to next step: If the test lamp illuminates 
  4. Ignition ON/Vehicle in service mode, test for 4.8 V - 5.2 V between the Drive Mode Switch 5 V Reference circuit terminal 11 and ground.
    • If less than 4.8 V 
    1. Test circuit 4109 for a short to ground.
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found.
    2. Test circuit 4109 for an open/high resistance.
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found.
    3. Replace the K20 Engine Control Module.
    • If greater than 5.2 V 
    1. Test circuit 4109 for a short to voltage.
      • If a short to voltage is found, repair the fault on the circuit.
      • Go to next step: If a short to voltage is not found.
    2. Replace the K20 Engine Control Module.
    • Go to next step: If between 4.8 V - 5.2 V 
  5. Disconnect the harness connector at the K20 Engine Control Module.
  6. Test for less than 1V in the Drive Mode Switch Signal circuit terminal 12 at the S48E Multifunction Switch - Center Console.
    • If 1 V or greater 

      Repair the short to voltage on the circuit.

    • Go to next step: If less than 1 V 
  7. Ignition/vehicle OFF.
  8. Disconnect the harness connector at the K20 Engine Control Module.
  9. Test for infinite resistance between the Drive Mode Switch Signal circuit terminal 12 at the S48 Multifunction Switch - Center Console and ground.
    • If less than infinite resistance 

      Repair the short to ground on the circuit.

    • Go to next step: If infinite resistance 
  10. Test the Drive Mode Switch Signal circuit for less than 2 Ω end to end.
    • If greater than 2 Ω 

      Repair the open in the Drive Mode Switch Signal circuit.

    • Go to next step: If less than 2 Ω 
  11. Test or replace the S48E Multifunction Switch - Center Console.
  12. Operate the vehicle with the Conditions for Running the DTC. You may also operate the vehicle with the conditions that you observed from the Freeze Frame/Failure Records data.
  13. Verify the DTC does not set.
    • If the DTC sets 

      Replace the K20 Engine Control Module.

    • Go to next step: If the DTC does not set 
  14. All OK.
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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.