DTC 59

Transmission Temperature Sensor Diagnostic Chart:

Transmission Temperature Sensor Circuit:

Circuit Description:
The Transmission Temperature Sensor (TTS) is a thermistor that controls the signal voltage to the PCM/TCM. The PCM/TCM applies 5 volts to the sensor on CKT 1227. When the transmission fluid is cold, the sensor resistance is high, therefore, the PCM/TCM will sense high signal voltage.

As the transmission fluid temperature warms, the sensor resistance becomes less and the voltage drops. At normal transmission operating temperature 100°C (212°F), the voltage will measure about 1.5 to 2.0 volts.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Code 59 will set if:
^ Signal voltage indicates a transmission temperature below -48°C (-54°F) for 1 second.

2. This test simulates a Code 58. If the PCM/TCM recognizes the low signal voltage (high temperature), and the "Scan" reads 151°C (304°F) or above, the PCM/TCM and wiring are OK.

3. This test will determine if CKT 1227 is open. There should be 5 volts present at the sensor connector if measured with a DVOM.


Diagnostic Aids:
"Scan" tool displays transmission temperature in degrees Centigrade. After transmission is running, the temperature should rise steadily to about 100°C (212°F) then stabilize.

A faulty connection or an open in CKT 455 or CKT 1227 will result in a Code 59.

The "Temperature to Resistance Value" scale at the right may be used to test the coolant sensor at various temperature levels to evaluate the possibility of a "skewed" (mis-scaled) sensor. A "skewed" sensor could result in firm garage shifts, or TCC enabled complaint.