Circuit Description
The Automatic Transmission Fluid Temperature (TFT) sensor is a thermistor. The TFT sensor is part of the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.). The Powertrain Control Module (PCM) supplies a 5-volt reference signal to the sensor on circuit 1227. When the transmission fluid is cold, the sensor resistance is high and the PCM senses a high signal voltage. As the transmission fluid warms, the sensor resistance lowers and the PCM senses lower voltage. The PCM uses the TFT reading in order to control the Torque Converter Clutch (TCC), line pressure adjustments, and temperature compensated shifts.
When the PCM detects a continuous short to ground in the TFT circuit or the TFT sensor, then DTC P0712 sets. DTC P0712 is a type D DTC.
Conditions for Setting the DTC
| • | The ignition switch is RUN position. |
| • | The TFT voltage is less than 0.33 volts for 10 seconds. |
Action Taken When the DTC Sets
| • | The PCM does not illuminate the Malfunction Indicator Lamp (MIL). |
| • | DTC P0712 is stored in the PCM history. |
| • | The PCM freezes shift adapts from being updated. |
| • | The PCM calculates transmission temperature based on engine coolant temperature, intake manifold air temperature, and engine run time. |
Conditions for Clearing the DTC
| • | A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported. |
| • | The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following conditions: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| • | When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change. |
Test Description
The numbers below refer to the Step numbers on the diagnostic table.
-
This Step tests the PCM's ability to detect an open circuit.
-
This Step tests the TFT sensor for correct resistance.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 2.3L | |||||
2 |
Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records for reference. The Clear Info function will erase the data. Does the scan tool display a transmission fluid temperature as specified? | 151°C (304°F) | Go to Diagnostic Aids | |||||
Does the scan tool display a transmission fluid temperature as specified? | -40°C (-40°F) | |||||||
4 | Inspect circuit 1227 from the engine 20-way connector to the PCM connector for a short to ground. Refer to Troubleshooting Procedures, Section 8. Did you find and correct the condition? | -- | ||||||
Is the resistance within the range specified for the given transmission temperatures? | 20°C (68°F) 3106-3923ohms 100°C (212°F) 164-190ohms | |||||||
6 | Replace the PCM. Refer to Section 6: Powertrain Control Module/EEPROM Replacement/Programming in Engine Controls - 2.3L Is the replacement complete? | -- | -- | |||||
7 | Inspect circuit 1227 from the Automatic Transmission 20-way connector to the TFT sensor connector for a short to ground. Refer to Troubleshooting Procedures, Section 8. Did you find and correct the condition? | -- | ||||||
8 | Replace the TFP Val. Position Sw. Refer to the Automatic Transmission Fluid Pressure Manual Valve Position Switch Replacement, in On-Vehicle Service. Is the replacement complete? | -- | -- | |||||
9 |
In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
