TM 9-2320-280-20-1 TRANSMISSION SYSTEM (4L80-E) DTC 73 Pressure Control Solenoid (PCS) Circuit Current Error (Force Motor Circuit) Circuit  Description: The  pressure  control  solenoid  is  a  TCM-controlled device used to regulate transmission line pressure. The TCM compares TP voltage, engine rpm and other inputs  to  determine  the  appropriate  line  pressure of a given load. The TCM will regulate the pressure by applying  a  varying  amperage  to  the  pressure  control solenoid.  The  applied  amperage  can  vary  from  0.1  to 1.1 amp. The TCM then monitors the amperage at the return  line. DTC 73 Will Set When: .  The  return  amperage  varies  greater  than 0.16  amps  from  the  commanded  amperage. . All conditions are met for 1 second. DTC 74 Transmission Input Speed Sensor (TISS) Circuit Circuit  Description: The TISS sensor consists of a permanent magnet surrounded by a coil of wire. As the forward clutch housing rotates, an AC voltage is induced in the circuit. The signal voltage and frequency vary directly with the forward clutch rotational speed. DTC 74 Will Set When” s Trans range not in park or neutral. . Engine speed greater than 300 rpm. l  Trans  output  speed  greater  than  200  rpm. l Trans input speed less than 50 rpm. . All conditions are met for 2 seconds. DTC 75 System Voltage Low Circuit  Description: Ignition  voltage  is  supplied  to  the  control  module  to indicate the status of the ignition switch. Battery voltage  is  supplied  to  the  control  module  to,  in  part, maintain memory of learned functions and parameters. DTC 75 Will Set When: l The ignition is “ON.” l  Ignition  feed  voltage  to  the  control  module  is less  than  the  graduated  scale  of: . -40°F (-40°C) = 7.3 volts. - 194°F (-90°C) = 10.3 volts. -  302°F  (-150°C)  =  11.7  volts. l Engine speed greater than 1000 rpm. l All conditions are met for 4 seconds. DTC 79 Transmission  Fluid  Overtemp Circuit  Description: The Transmission Fluid Temperature (TFT) sensor is a thermistor that controls the signal voltage to the TCM. The TCM supplies a 5-volt reference signal  to  the  sensor  on  CKT  923A.  When  the transmission  fluid  is  cold,  the  sensor  resistance  is high and the TCM will sense high signal voltage. As  the  transmission  fluid  temperature  warms  to normal  transmission  operating  temperature  212°F (100°C), the sensor resistance becomes less and the voltage decreases to approximately 1.5 to 2.0 volts. DTC 79 Will Set When: l Trans fluid temp greater than 295°F (146°C). l All conditions are met for 30 minutes. 2-425