CODE 58, TRANSMISSION FLUID TEMPERATURE HIGH
The transmission fluid temperature sensor is a thermistor which controls the signal voltage to the PCM/TCM. The PCM/TCM applies and monitors voltage to the sensor. When transmission fluid is cold, sensor resistance is high; therefore, the PCM/TCM will see high signal voltage. As the transmission fluid warms up, sensor resistance and voltage will drop. At normal transmission operating temperature of 212°F (100°C), voltage will be about 1.5-2.0 volts.
Note. Test numbers refer to numbers on diagnostic chart.
- Code 58 will set if signal voltage indicates a transmission fluid temperature greater than 305°F (151°C) for one second.
- This test determines if circuit is shorted to ground, which will result in conditions for Code 58.
CODE 59, TRANSMISSION FLUID TEMPERATURE LOW
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.
Note. Test numbers refer to numbers on diagnostic chart.
- Code 59 will set if signal voltage indicates a transmission fluid temperature less than -34°F (-37°C) for one second.
- 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.
- This test determines if signal circuit is open. There should be 5 volts present at the sensor connector if measuring with a DVOM.
CODE 79, TRANSMISSION FLUID TEMPERATURE HIGH
The transmission fluid temperature sensor is a thermistor which controls the signal voltage to the PCM/TCM. The PCM/TCM applies and monitors voltage to the sensor. When transmission fluid is cold, sensor resistance is high; therefore, the PCM/TCM will see high signal voltage. As the transmission fluid warms up, sensor resistance and voltage will drop. At normal transmission operating temperature of 212°F (100°C), voltage will be about 1.5-2.0 volts.
Note. Test numbers refer to numbers on diagnostic chart.
- Code 79 will set if signal voltage indicates a transmission fluid temperature greater than 151°C for one second.
- This test determines if circuit is shorted to ground, which will result in conditions for Code 79.