VT25-E Automatic Transmission

VT25-E AUTOMATIC TRANSMISSION

DTC P0712

Test 1-8:

Circuit Description with VT25-E Automatic Transmission
The automatic transmission fluid temperature (TFT) sensor is part of the control solenoid valve assembly. The TFT sensor is a thermistor, or a resistor that changes resistance when the temperature changes. The sensor has a negative-temperature coefficient. This means that as the temperature increases, the resistance decreases, and as the temperature decreases, the resistance increases. The transmission control module (TCM) supplies a 5 volt reference signal to the sensor and measures the voltage drop in the circuit. When the transmission fluid is cold, the sensor resistance is high and the TCM detects high signal voltage. As the fluid temperature increases, the resistance of the sensor decreases, which lowers the signal voltage.

If the TCM detects a short to ground in the TFT sensor or signal circuit, then DTC P0712 sets. DTC P0712 is a type C DTC.

Conditions for Running The DTC
The engine speed is greater than 500 RPM for 5seconds.

Conditions for Setting The DTC
The TCM detects a transmission fluid temperature of 151°C (304°F) or greater for 2 seconds.

Action Taken When the DTC Sets
^ The TCM does not request the ECM to illuminate the malfunction indicator lamp (MIL).
^ SERVICE VEHICLE message displays on the driver information center (DIC).
^ The TCM calculates a default transmission fluid temperature based on engine coolant temperature, intake air temperature and engine run time.
^ The TCM freezes garage shift transmission adaptive functions.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
^ The TCM stores DTC P0712 in TCM history.

Conditions for Clearing the DIC/DTC
^ The TCM clears the DIC message when the condition no longer exists.
^ A scan tool can clear the DIC/DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non emission related diagnostic fault occurring.
^ The TCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

Diagnostic Aids
^ Inspect the connectors at the TCM, the transmission, and all other circuit connecting points for an intermittent condition.
^ Inspect the circuit wiring for an intermittent condition.

Test Description
The numbers refer to the step numbers on the diagnostic table.
3. This step tests the ability of the TCM to detect an open circuit. If the TCM recognizes the open, this eliminates the TCM and the wiring up to the transmission connector. The fault must be internal to the transmission.
5. Because the TFT is an integral part of the control solenoid valve assembly, the control solenoid valve assembly must be replaced.