Diagnostic Aids

Scan tool displays transmission fluid temperature in degrees Centigrade. After transmission has been in operation, temperature should rise steadily to about 212°F (100°C) then stabilize. A faulty connection or an open in circuit No. 455/452 or circuit No. 1227 will result in a DTC 59. Test transmission sensor at various temperature levels to determine if sensor is out of calibration. See TRANSMISSION SENSOR - TEMP TO RESISTANCE chart. An out-of-calibration sensor could result in firm shifts or TCC enabled complaint.

Fig 1: DTC 59 Schematic - 1993

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC 59 Flow Chart - 1993

Courtesy of GENERAL MOTORS CORP.