Diagnostic Aids

Check harness routing for a potential short to ground in circuit No. 1227. Scan tester displays transmission fluid temperature in degrees Centigrade. After transmission is running, the temperature display should rise steadily to about 100°C then stabilize. Test the 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 delayed shifts or TCC enabled complaint. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.

Fig 1: CODE 79, Schematic, Trans. Fluid Overtemp (Astro, Safari & "C" & "K" Series)

Courtesy of GENERAL MOTORS CORP.

Fig 2: CODE 79, Schematic, Trans. Fluid Overtemp ("G" Series)

Courtesy of GENERAL MOTORS CORP.

Fig 3: CODE 79, Flowchart, Transmission Fluid Overtemp

Courtesy of GENERAL MOTORS CORP.