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For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 LeSabre 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input

Object Number: 423306 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 C 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 less than 0.2 volts 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 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.

Conditions for Clearing the DTC
    • A scan tool clears the DTC from PCM history.
    • The PCM clears the DTC from PCM history if the vehicle completes 40 consecutive 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 ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
    • Inspect the connectors at the controller, the component and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Wiring Systems.

Test Description

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

  1. This step tests the PCM's 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. Using the Clear Info function erases the failure records from the PCM.

  3. Record the failure records.
  4. Clear the DTCs.
  5. Select Scan Tool TFT sensor.

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

0.2 volts

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 (additional DTCs will set).
  3. Turn the ignition switch to the RUN position.

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

4.92 volts

Go to Step 5

Go to Step 4

4

Inspect circuit 1227 from the engine 20-way connector to the PCM connector for a short to ground.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Was the condition found?

--

Go to Step 8

Go to Step 11

5

  1. Install the J 44152 jumper harness to the transmission side of the 20-way connector.
  2. Using a J 35616 connector test adapter kit, connect the J 39200 digital multimeter (DMM) from terminal L to terminal M and measure the resistance.

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 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 Circuit Testing and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 12

--

9

Replace the TFT sensor.

Refer to Solenoids and Wiring Harness Replacement .

Is the replacement complete?

--

Go to Step 12

--

10

Replace the automatic transmission wiring harness.

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