AF23-5 Automatic Transaxle

AF23-5 AUTOMATIC TRANSAXLE

DTC P0712

Test 1-8:

Circuit Description with AF23-5 Automatic Transaxle
The automatic transmission fluid temperature (TFT) sensor is part of the automatic transmission internal wiring harness assembly. The TFT sensor is a thermistor, or a resistor that changes value 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 A DTC.

Conditions for Running The DTC
^ Trans. Protection Mode is OFF.
^ The engine run time is 5 seconds or greater.
^ The ignition voltage is 8-18 volts.

Conditions for Setting The DTC
The TCM detects a transmission fluid temperature of 150°C (302°F) or more for 5 minutes.

Action Taken When the DTC Sets
^ The TCM requests the EGM to illuminate the malfunction indicator lamp (MIL).
^ DTC P 1719 is disabled.
^ No lock-up slip neutral control or uphill/downhill control until transmission fluid temperature is greater than 40°C (104°F) for 5 seconds.
^ The TCM discontinues updating the transmission adaptive pressure (TAP) memory cells, until engine run time is at least 30 minutes.
^ The TCM uses 30°C (86°F) as a default transmission fluid temperature.
^ The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.
^ The TCM stores DTC P0712 in TCM history.

Conditions for Clearing the MIL/DTC
^ The TCM turns OFF the MIL request during the third consecutive trip in which the diagnostic test runs and passes.
^ A scan tool can clear the DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
^ The TCM cancels the DTC default actions when the fault no longer exists and the DTC passes. The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM.

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 transmission wiring, the entire harness must be replaced.