GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1997 🢒 GMC P42 Commercial Chassis 🢒 Brakes 🢒 Air Brakes 🢒 Low Air Pressure Switch
  1. Set the parking brake.
  2. Drain the air reservoirs. Refer to Draining Reservoirs .
  3. Start the engine. Run the engine at fast idle.
  4. Verify that the low pressure tone alarm is on.
  5. If the audible warning alarm is not on when you first charge the system, check the audible warning circuit. Refer to Audible Warning Cell 76. Replace the low pressure switch if necessary. Refer to Low Air Pressure Warning Switch .
  6. The low pressure tone alarm should turn off when the dual air pressure gauge indicates 415 kPa (60 psi).
  7. If the audible warning alarm does not turn off, check the audible warning circuit. Refer to Audible Warning Cell 76. Replace the low pressure switch if necessary. Refer to Low Air Pressure Warning Switch .