Powertrain Controls - ECM/PCM

Diagnostic Trouble Code 58:

Transmission Range 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 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 on terminal "D28."

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. With a Diagnostic Trouble Code (DTC) 79 also set, check the transmission cooling system.

DTC 58 WILL SET WHEN
Signal voltage indicates TFT greater than 151°C (306°F) for at least 1 second.

ACTION TAKEN (PCM DEFAULT)
When DTC 58 is set, the transmission will use a warm value for operation, but the scan tool will display the actual fluid temperature. 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
Numbers below refer to circled numbers 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
Harness Routing
Check harness routing for a potential short to ground in CKT 1227.

Scan Tool Diagnosis
Scan tool TFT displays should rise steadily to about 100°C (212°F) then stabilize.

Temperature To Resistance Correlation
The temperature to resistance value scale may be used to test the transmission sensor at the various temperature levels to evaluate the possibility of a "skewed" sensor. A "skewed" sensor could result in delayed garage shifts or transmission Torque Converter Clutch (TCC) enabled complaints.