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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 787 (Antilock Brake System With TCVS & VSES) >> Diagnostic Information and Procedures >> Brake Pressure Modulator Valve Hydraulic Testing >> TC Isolation Valve Test Procedure

TC Isolation Valve Test Procedure

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 Chevrolet Tahoe, 2003 Chevrolet Suburban, and 2003 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn OFF the ignition.
  2. Disconnect the brake switch harness connector.
  3. Raise the vehicle so that all four wheels are about 15 cm (6 in) off of the floor. Refer to LIFTING AND JACKING THE VEHICLE in General Information. 
  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.
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