LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 1993 >> Forward Control 7.4 N >> Repair and Diagnosis (Single Page) >> Transmission >> Automatic Trans >> Automatic Transmission - Diagnosis - 4L80-E >> Diagnostic Charts >> DTC 79, Transmission Fluid Temperature Sensor Circuit (High Temperature Indicated) 1994 >> Diagnostic Aids

Diagnostic Aids

Check harness routing for potential short to ground in circuit No. 1227. Scan tool displayed temperature should rise steadily to about 212°F (100°C), then stabilize. Test transmission sensor at various temperature levels to determine if sensor is out of calibration. See TEMPERATURE-TO-RESISTANCE VALUES (DTC 79) table. An out-of-calibration sensor could result in firm shifts or TCC enable complaint.

TEMPERATURE-TO-RESISTANCE VALUES (1) (DTC 79)

Temperature °F (°C) Ohms
300 (150) 43-52
248 (120) 90-110
212 (100) 158-196
160 (70) 410-524
104 (40) 1260-1660
70 (20) 2981-4018
15 (-10) 13,366-18,770
0 (-18) 23,458-33,524
-40 (-40) 80,965-120,123
(1) Measure resistance across sensor terminals.
Fig 1: DTC 79 Schematic - 1994
G94H38387Courtesy of GENERAL MOTORS CORP.
Fig 2: DTC 79 Flow Chart - 1994
G94I38388Courtesy of GENERAL MOTORS CORP.