GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 TopKick C-Series Commercial (Cutaway) C4/C5 🢒 Brakes 🢒 Air Brakes 🢒 Trailer Brake Control Valve Operational Check
  1. Block the wheels.
  2. Test the vehicle dual air pressure gauge with the test gauge.
  3. Install the test air pressure gauge in the valve delivery line.
  4. Start the engine.
  5. Charge the system air pressure to the governor cut-out point.

    6. Object Number: 227705 Size: SH
  6. Move the trailer brake control valve lever to the full OFF position.

    7. Object Number: 202795 Size: MH
  7. Check that the test air pressure gauge indicates zero air pressure.
  8. Repair or replace the control valve (5) if the air pressure does not indicate zero.

    9. Object Number: 227705 Size: SH
  9. Move the trailer brake control valve lever to the full ON position.

    10. Object Number: 202795 Size: MH
  10. Check that the test air pressure gauge indicates the same air pressure as the dual air pressure gauge.
    11. • If the pressure is not the same, adjust the valve (5). Refer to Valve Adjustment.
    •  If the valve (5) does not deliver full pressure after the adjustment, replace the valve (5).

    Object Number: 227705 Size: SH
  11. Move the trailer brake control valve lever to several intermediate positions.
  12. Drain the air system reservoirs. Refer to Air Brake Reservoir Draining .
  13. Remove the test air pressure gauge.
  14. Check the operation of the brakes.
  15. Remove the wheel blocks.