With 4L80E Transmission

Transmission Fluid Temperature (TFT) Sensor Circuit High (Low Temp Ind):

Temperature Fluid Temperature (TFT) Sensor Circuit High (Low Temp Ind):

CIRCUIT DESCRIPTION
The Transmission Fluid Temperature (TFT) sensor is a thermistor that controls the signal voltage to the Powertrain Control Module (PCM). The PCM supplies a 5 volt reference signal to the sensor on CKT 1227. When the transmission fluid is cold, the sensor resistance is high and the PCM will sense high signal voltage.
As the transmission fluid temperature warms to normal transmission operating temperature 100°C (212°F), the sensor resistance becomes less and the voltage decreases to approximately 1.5 to 2.0 volts.

DIAGNOSTIC TROUBLE CODE (DTC) 59 WILL SET WHEN
- Signal voltage indicates TFT less than -40°C (-40°F).
- All conditions met for 1 second.

ACTION TAKEN (PCM WILL DEFAULT TO)
The PCM will use a warm default trans fluid temperature value.

DTC 59 WILL CLEAR WHEN
The fault condition(s) no longer exist.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This checks for entire circuit and indicates whether the malfunction is present.
2. This test simulates a DTC 58. If the PCM recognizes the low signal voltage (high temperature), and the scan displays 151°C (305°F) or greater, the PCM and wiring are OK.
3. This test checks if CKT 1227 is open. There should be 5 volts present at the sensor connector if measured with J 39200.

DIAGNOSTIC AIDS
- Scan tool displays transmission fluid temperature in degrees. After transmission is operating, 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 can result in a DTC 59.
- The Temperature to Resistance Value scale may be used to check the TFT sensor at various temperature levels to evaluate the possibility of a "skewed" (mis-scaled) sensor. A "skewed" sensor can result in firm shifts, or Torque Converter Clutch (TCC) complaints.