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For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Regal (China) (CNG) 🢒 Engine 🢒 Engine Controls - 3.0L (L46) 🢒 DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input

Object Number: 362641 Size: MF
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The automatic transmission fluid temperature (TFT) sensor is a negative coefficient thermistor whose resistance value changes based on temperature. The PCM provides a 5 volt reference to the sensor on circuit 1227. A high fluid temperature or a short to ground on circuit 1227 results in low signal voltage. The TFT sensor operating range is -40 to +151°C (-40 to +304°F).

If the PCM detects a continuous short to ground in TFT sensor circuit 1227, then DTC P0712 sets. DTC P0712 is a type D DTC.

Conditions for Running the DTC

The system voltage is 9-18 volts.

Conditions for Setting the DTC

The PCM detects a TFT sensor voltage of 0.2 volts or less for 10 seconds.

Action Taken When the DTC Sets
    • The PCM does not turn on the malfunction indicator lamp (MIL).
    • The PCM freezes shift adapts.
    • The PCM calculates a default TFT from the ECT sensor and the IAT sensor.
    • The PCM stores DTC P0712 in PCM history.

Conditions for Clearing the DTC
    • A scan tool clears the DTC from the PCM history.
    • The PCM clears the DTC from the PCM history if the vehicle completes 40 consecutive warm-up cycles without a diagnostic fault occurring.
    • The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
    • Inspect the wiring at the PCM, the transmission 20-way connector and all other circuit connecting points for the following conditions:
       - A backed out terminal
       - A damaged terminal
       - Reduced terminal tension
       - A chafed wire
       - A broken wire inside the insulation
       - Moisture intrusion
       - Corrosion
    • When diagnosing for an intermittent short to ground or short to power, massage the wiring harness while watching the test equipment for a change.
    • Test the TFT sensor at various temperature levels to evaluate the possibility of a skewed (mis-scaled) sensor. Refer to the Temperature vs Resistance table.

Test Description

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

  1. This step tests the PCMs ability to detect an open circuit.

    2.

  2. This step tests the TFT sensor for correct resistance.

DTC P0712 TFT Sensor Circuit Low

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls

2
  1. Install the Scan Tool .
  2. Turn the ignition switch to the RUN position.

    3. Important: Before clearing the DTCs, use the Scan Tool in order to record the Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the PCM.

  3. Record the Failure Records.
  4. Clear the DTCs.
  5. Monitor TFT sensor on the Scan Tool .

Does the Scan Tool display a TFT sensor voltage less than the specified value?

0.2 V

Go to Step 3

Go to Diagnostic Aids

3

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the transmission 20-way connector.

    3. Important: Additional DTCs will set.

  3. Turn the ignition switch to the RUN position.

Does the Scan Tool display a TFT sensor voltage greater than the specified value?

4.9 volts

Go to Step 5

Go to Step 4

4

Inspect circuit 1227 (YEL/BLK) from the engine 20-way connector to the PCM connector for a short to ground.

Refer to General Electrical Diagnosis in Wiring Systems.

Was a condition found?

--

Go to Step 8

Go to Step 11

5

  1. Connect the J 39775 jumper harness to the transmission side of the 20-way connector.
  2. Using the J 35616-A connector test adapter kit, connect the J 39200 digital multimeter (DMM) from terminal L to terminal M and measure the resistance.

    3. Refer to Automatic Transmission Inline Harness 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 terminal L and a good ground on the transmission case.

Is the resistance less than the specified value?

1000 ohms

Go to Step 10

Go to Diagnostic Aids

7
  1. Disconnect the TFT sensor from the automatic transmission wiring harness.
  2. Measure the resistance between terminal L and terminal M of the J 39775 jumper harness.

Is the resistance less than the specified value?

1000 ohms

Go to Step 10

Go to Step 9

8

Repair the wiring as necessary.

Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 12

--

9

Replace the TFT sensor.

Refer to Fluid Temperature Sensor Replacement .

Is the replacement complete?

--

Go to Step 12

--

10

Replace the automatic transmission wiring harness assembly.

Refer to Solenoids and Wiring Harness Replacement .

Is the replacement complete?

--

Go to Step 12

--

11

Replace the PCM.

Refer to Powertrain Control Module Replacement/Programming in Engine Controls.

Is the replacement complete?

--

Go to Step 12

--

12

Perform the following procedure In order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • Turn the ignition switch to the RUN position.
    • The TFT signal voltage must be greater than 0.2 volts for 10 seconds.
  4. Select Specific DTC.
  5. Enter DTC P0712.

Has the test run and passed?

--

System OK

Go to Step 1