Circuit Description
The automatic transmission fluid temperature (TFT) sensor is a thermistor. The TFT sensor is part of the automatic transmission fluid pressure (TFP) manual valve position switch. The transmission control module (TCM) supplies a 5 volt reference signal to the sensor. When the transmission fluid is cold, the sensor resistance is high and the TCM senses a high signal voltage. As the transmission fluid warms, the sensor resistance lowers and the TCM senses lower voltage. The TCM uses the TFT reading in order to control the torque converter clutch (TCC), line pressure adjustments, and temperature compensated shifts.
When the TCM detects a continuous short to ground in the TFT circuit or the TFT sensor, then DTC P0712 sets. DTC P0712 is a type C DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Voltage
Conditions for Running the DTC
The engine is running for 5 seconds.
Conditions for Setting the DTC
The TFT is greater than 150°C (302°F) for 12 seconds.
Action Taken When the DTC Sets
| • | The TCM does not request the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL). |
| • | The TCM freezes transmission adaptive functions. |
| • | The TCM calculates a default transmission fluid temperature based on engine coolant temperature, intake manifold air temperature, and engine run time. |
| • | 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 DTC
| • | A scan tool can clear the 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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the ability of the TCM to detect an open circuit.
-
This step tests the TFT sensor for correct resistance.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Important: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the TCM. Does the scan tool display a TFT sensor reading less than the specified value? | 150°C (302°F) | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
Does the scan tool display a TFT sensor reading less than the specified value? | -39°C (-38°F) | Go to Step 5 | Go to Step 4 | |
4 | Test the signal circuit of the TFT sensor for a short to ground between the TCM connector and the AT inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance within the range specified for the given transmission temperatures? | 20°C (68°F) 3,106-3,923 ohms 100°C (212°F) 164-190 ohms | Go to Step 6 | Go to Step 7 | |
6 | Measure the resistance between the TFT sensor signal circuit of the J 44152 and a good ground. Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance less than the specified value? | 1,000 ohms | Go to Step 9 | Go to Testing for Intermittent Conditions and Poor Connections |
7 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance between less than the specified value? | 1,000 ohms | Go to Step 9 | Go to Step 8 |
8 | Replace the TFP manual valve position switch. Refer to Transmission Fluid Pressure Manual Valve Position Switch Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- |
9 | Replace the automatic transmission wiring harness. Refer to Wiring Harness Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- |
10 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 11 | -- |
11 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 12 | Go to Step 2 |
12 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
