The automatic transmission fluid temperature (TFT) sensor is a negative coefficient thermistor whose resistance value changes based on temperature. The powertrain control module (PCM) 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 +151°C (-40 to +304°F).
If the PCM detects a continuous short to ground in the TFT sensor circuit, then DTC P0712 sets. DTC P0712 is a type C DTC.
• | No Trans. Temp. DTCs P0218, P0711 or P0713. |
• | The engine run time is greater than 5 seconds. |
The PCM detects a TFT of 149°C (300°F) or greater for 10 seconds.
• | The PCM does not illuminate the malfunction indicator lamp (MIL). |
• | The PCM calculates a default transmission fluid temperature based on engine coolant temperature, intake air temperature and engine run time. |
• | The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records. |
• | The PCM stores DTC P0712 in PCM history. |
• | A scan tool can clear the DTC. |
• | The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring. |
• | The PCM cancels the DTC default actions when the fault no longer exists and the DTC passes. |
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 equal to or greater than 149°C (300°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 - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls | ||||
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 PCM. Does the scan tool display a Trans. Fluid Temp. less than the specified value? | 149°C (300°F) | Go to Intermittent Conditions in Engine Controls | 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 PCM connector C3 and the AT inline 20-way connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. 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 Intermittent Conditions in Engine Controls | ||||
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, GM P/N 15320475, and the Automatic Transmission Wiring Extension Harness Assembly, GM P/N 15320478. In order to avoid the unnecessary replacement of parts, only replace the Automatic Transmission Wiring Harness Assembly, GM P/N 15320475. 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 PCM. Refer to Powertrain Control Module Replacement in Engine Controls. 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? | -- | Go to Diagnostic Trouble Code (DTC) List in Engine Controls | System OK |