2008 Chevrolet Chevy Express G2500, Van Cargo Extended, 6.0 KFACTORY OEM SERVICE PROCEDURE

TC Isolation Valve Test Procedure

  1. Turn OFF the ignition.
  2. Disconnect the brake switch harness connector.
  3. Raise the vehicle so that all 4 wheels are about 15 cm (6 in) off of the floor. Refer to Lifting and Jacking the Vehicle .
  4. Ensure that the park brake is released.
  5. Turn ON the ignition.
  6. Ensure that the transmission is in neutral (N).
  7. Select the VSES Special Functions menu on the scan tool.
  8. Select either the Left Front Brake Apply or the Right Front Brake Apply, whichever wheel has the most convenient access for you.
  9. Press the Apply key on the scan tool.
  10. Listen for the precharge pump to activate for approximately 2 seconds.
  11. Immediately verify brake activation at the wheel by attempting to turn the wheel by hand.
  12. Continue attempting to turn the wheel by hand and ensure the wheel remains locked for 9 seconds after the precharge pump turns OFF.
  13. Verify that the brake releases quickly when the 9 second pressure hold is terminated.
  14. Select either the Left Rear Brake Apply or the Right Rear Brake Apply, whichever wheel has the most convenient access for you.
  15. Repeat steps 11, 12, and 13 for the rear wheel being tested.
  16. Turn OFF the ignition.
  17. Reconnect the brake switch harness connector.
Factory Service Tools

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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.

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