TM 9-2320-302-10 0010 00-2 Table 1. Troubleshooting Procedures - Continued. MALFUNCTION TEST OR INSPECTION CORRECTIVE ACTION 2.  Air System Loses Pressure During Vehicle   Operation   or   Low   Air Pressure Warning Light and Buzzer  Come  On  During  Vehicle Operation - Continued. 1.  Ensure trailer air supply  control  knob  is pulled out (OFF). Operate    engine    until warning light and buzzer go off and release  parking  brake. Stop   engine   and   note reservoir pressure. Fully   press   and   hold service brake pedal for two minutes. Have crewmember check for leaks. Reservoir pressure     loss     during two minute period should not exceed 5 psi (34 kPa). Close air reservoir draincocks.   If   leaks   are present, notify Unit Maintenance. NOTE Any change in pressure on brake pedal will cause a change in air pressure reading. 2.  Push  trailer  air  supply control knob in (ON) to charge   semitrailer   air reservoirs    and    repeat step 1. Have crewmember check semitrailer    for    leaks. Pressure    loss    should not   exceed   5   psi   (34 kPa) in two minutes. If air leaks are present or reservoir pressure loss exceeds 5 psi (34 kPa) in two minutes, trouble- shoot semitrailer. 3.  Trailer   Brakes   Will   Not   Apply When  Pedal  or  Hand  Control  on Steering Column is Used. Check  intervehicular  air hoses for proper connections to semitrailer. Connect air hoses. 4.  Trailer Brakes Will Not Release. 1.  Check position of trailer brake hand control. Move  control  to  forward (OFF) position. 2.  Check position of trailer air supply control knob. Push knob in (ON).