Transaxle Fluid Temperature (TFT) Sensor

2006 Chevrolet Cobalt SS, 4D Sedan, StandardSECTION Transaxle Fluid Temperature (TFT) Sensor
WARNING: This page is about a different car, the 2005 Saturn L300. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Locating Transaxle Fluid Temperature (TFT) Sensor
GM893174Courtesy of GENERAL MOTORS CORP.

The transaxle fluid temperature (TFT) sensor is a negative temperature coefficient thermistor that provides information to the TCM regarding transaxle fluid temperature. The temperature sensor is integrated in transaxle fluid pressure switch assembly which is bolted to the control valve body. The sensor monitors main line pressure from the inside of the control valve body in order to determine the operating temperature of the transaxle fluid. The sensor uses an O-ring seal to maintain fluid pressure in the control valve body.

The internal electrical resistance of the sensor varies in relation to the operating temperature of the transaxle fluid. The TCM sends a 5-volt reference signal to the temperature sensor, then measures voltage drop in the electrical circuit. A lower fluid temperature creates a higher resistance in the temperature sensor, thereby measuring a higher voltage signal.

The TCM measures this voltage as another input to help control line pressure, shift schedules and TCC apply. When the TFT reaches 140°C (284°F), the TCM enters hot mode. Above this temperature the TCM modifies the transaxle shift schedules and TCC apply in an attempt to reduce fluid temperature by reducing the amount of heat generated by the transaxle. During hot mode the TCM applies TCC at all times in Third and Fourth gears. Also, the TCM performs the 2-3 and 3-4 shifts earlier in order to help reduce heat generated in transaxle fluid.

TFT Sensor - Temperature to Resistance

TFT Sensor - Temperature-To-Resistance

°C (°F) R Low (ohms) R High (ohms)
0°C (32°F) 7987 10859
10°C (50 °F) 4934 6407
20°C (68 °F) 3106 3923
30°C (86 °F) 1991 2483
40°C (104 °F) 1307 1611
50°C (122 °F) 878 1067
60°C (140 °F) 605 728
70°C (158 °F) 425 507
80°C (176 °F) 304 359
90°C (194 °F) 221 259
100°C (212 °F) 163 190
RENDER: 1.0x

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