Code 59, Transmission Fluid Temperature Low: Notes

The transmission fluid temperature sensor is a thermistor which controls the signal voltage to PCM/TCM. The PCM/TCM applies and monitors 5 volts to the sensor. When transmission fluid is cold, sensor resistance is high; therefore, the PCM/TCM will see high signal voltage. As transmission fluid temperature warms up, sensor resistance and voltage drop. At normal transmission operating temperature of 212°F (100°C), voltage will be about 1.5-2.0 volts.

1. Code 59 will set if signal voltage indicates a transmission fluid temperature less than -34°F (-37°C) for one second.
2. This test simulates Code 58. If PCM/TCM recognizes low signal voltage (high temperature) and scan tester reads 305°F (151°C) or greater, PCM/TCM and wiring are okay.
3. This test determines if signal circuit is open. There should be 5 volts present at the sensor connector if measuring with a DVOM.