Circuit Description
The automatic transmission fluid temperature (TFT) sensor is a negative coefficient thermistor whose resistance value changes based on temperature. The transmission control module (TCM) provides a 5 volt reference to the sensor. A high fluid temperature or a short to ground on the signal circuit results in low signal voltage. The TFT operating range is -40 to +150°C (-40 to +302°F).
If the TCM detects a continuous short to ground in the TFT sensor circuit, 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
| • | No Trans. Temp. DTCs P0218, P0711 or P0713. |
| • | The engine run time is greater than 5 seconds. |
Conditions for Setting the DTC
The TCM detects a TFT of 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 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
| • | 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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies DTC P0712 by indicating a short to ground. If the scan tool does not display a transmission fluid temperature greater than 150°C (302°F), then the DTC is intermittent.
-
This step isolates the transmission. If the scan tool displays a transmission fluid temperature less than -38°C (-36°F), then the engine wiring harness is good.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 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 Trans. Fluid Temp. 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 Trans. Fluid Temp. 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 Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 | ||||
5 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Does the resistance measure within the range specified for the given transmission temperatures? | 20°C (68°F) 2981-4,018 ohms 80°C (176°F) 293-372 ohms | Go to Step 6 | Go to Step 7 | ||||
6 | Measure the resistance between terminal L of the J 44152 and ground. Refer to Automatic Transmission Inline 20-Way Connector End View . Does the resistance measure less than the specified value? | 100 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 . Does the resistance measure between terminal L and any other terminal less than the specified value? | 100 ohms | Go to Step 9 | Go to Step 8 | ||||
8 | Replace the TFT sensor. Refer to Control Valve Upper Body Disassemble in the 4T80-E section of the Transmission Unit Repair Manual. Did you complete the replacement? | -- | Go to Step 11 | -- | ||||
9 |
Important: The automatic transmission wiring harness consists of two separate harnesses, the Automatic Transmission Wiring Harness Assembly and the Automatic Transmission Wiring Extension Harness Assembly. In order to avoid the unnecessary replacement of parts, only replace the Automatic Transmission Wiring Harness Assembly. Replace the automatic transmission wiring harness. Refer to Input Speed Sensor and Wiring Harness Removal in the 4T80-E section of the Transmission Unit Repair Manual. Did you complete the replacement? | -- | Go to Step 11 | -- | ||||
10 | Replace the TCM. Refer to Control Module References . 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 |
