GM Service Manual Online
For 1990-2009 cars only

Object Number: 1746367  Size: MF
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Control Module References

Circuit Description

The automatic transmission fluid temperature (TFT) sensor is part of the automatic transmission fluid pressure (TFP) manual valve position switch. 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 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 run time is greater than 5 seconds.

Conditions for Setting the DTC

The TCM detects a transmission fluid temperature of 150°C (302°F) or more 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 commands elevated line pressure.
    • 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 a Failure Record.
    • 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.

Diagnostic Aids

    • The scan tool displays the transmission fluid temperature in degrees. After the transmission is operating, the fluid temperature should rise steadily to a normal operating temperature, then stabilize.
    • Verify the customer's driving habits, trailer towing, etc. Trailer towing should occur in D3.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for a short to ground condition.

  2. This step tests for an internal fault within the transmission by creating an open.

DTC P0712

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Inspect for correct transmission fluid level.

Refer to Transmission Fluid Check .

Did you perform the fluid checking procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. 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.

  4. Record the DTC Failure Records.
  5. Clear the DTC.

Does the scan tool displays a TFT Sensor signal voltage greater than the specified value?

0.2 V

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the AT inline 20-way connector, additional DTCs may set.
  3. Turn ON the ignition, with the engine OFF.

Does the scan tool display a TFT Sensor signal voltage greater than the specified value?

4.92 V

Go to Step 5

Go to Step 7

5

  1. Install the J 44152 Jumper Harness (20 pins) on the transmission side of the AT inline 20-way connector.
  2. Using the DMM and the J 35616 GM Terminal Test Kit, measure the resistance the TFT sensor signal and low reference circuits of the J 44152 .
  3. Refer to Testing for Continuity .

Refer to Automatic Transmission Inline 20-Way Connector End View .

Does the resistance measure within the specified range?

3088-3942 ohms at 20°C (68°F)

159-198 ohms at 100°C (212°F)

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 6

6

Test the signal circuit of the TFT sensor for a short to ground between the AT inline 20-way connector and the TFT sensor.

Refer to Testing for Short to Ground .

Did you find a short to ground condition?

--

Go to Step 9

Go to Step 8

7

Test the signal circuit of the TFT sensor for a short to ground between the TCM 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

8

Replace the TFT sensor, this sensor is part of the TFP manual valve position switch.

Refer to Valve Body and Pressure Switch Replacement .

Did you complete the replacement?

--

Go to Step 11

--

9

Replace the AT wiring harness.

Refer to Valve Body and Pressure Switch 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:

  1. Select DTC.
  2. Select Clear Info.
  3. Turn ON the ignition, with the engine OFF.
  4. Verify that the scan tool indicates a TFT Sensor signal voltage greater than 0.2 volts for 10 seconds.
  5. Select Specific DTC.
  6. Enter DTC P0712.

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 - Vehicle

System OK