With 4L60E Transmission

DTC 58 Transmission Fluid Temperature (TFT) Sensor Circuit Low:

Transmission Range (TR) Pressure Switch Assembly Circuit:

CIRCUIT DESCRIPTION
The Transmission Fluid Temperature (TFT) sensor is a thermistor within the Transmission Range (TR) pressure switch assembly, that controls the signal voltage to the Powertrain Control Module (PCM). The PCM applies voltage on CKT 1227 to the sensor. 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 the normal transmission operating temperature of 100°C (212°F), the sensor resistance becomes less and the voltage decreases to 1.5 to 2.0 volts. With a DTC 79 also set, check the transmission cooling system.

DIAGNOSTIC TROUBLE CODE (DTC) 58 WILL SET WHEN
Signal voltage indicates TFT greater than 151°C (306°F) for 1 seconds.

ACTION TAKEN (PCM will default to)
When DTC 58 is set, the transmission will use a warm value for operation, but the scan tool will display the actual fluid temperature. The Torque Converter Clutch (TCC) solenoid will be "ON" in third, and fourth gears. The shifts will occur early. DTC 58 will be stored in the PCM memory but will not turn "ON" the Malfunction Indicator Lamp (MIL).

DTC 58 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 test checks for a short to ground or a skewed sensor.
2. This test checks for an internal fault within the transmission by creating an open.

DIAGNOSTIC AIDS
Check harness routing for a potential short to ground in CKT 1227. Scan tool TFT display should rise steadily to about 100°C (212°F) then stabilize.
Refer to Intermittants. Testing and Inspection
The temperature to resistance value scale may be used to test the TFT sensor at the various temperature levels to evaluate the possibility of a "skewed" sensor. A "skewed" (mis-scaled) sensor could result in delayed garage shifts or Torque Converter Clutch (TCC) complaints.