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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Eldorado 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T80-E 🢒 DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input

Object Number: 347381 Size: SF
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 1227/452. A high fluid temperature or a short to ground on circuit 1227/452 results in low signal voltage. The TFT operating range is -40 to +151°C (-40 to +305°F).

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

Conditions for Running the DTC
    • The ignition switch is in the RUN position.
    • The system voltage is 10-17 volts.

Conditions for Setting the DTC

The PCM detects a TFT of 148°C (298°F) or greater (0.08 volts or less) for 5 seconds.

Action Taken When the DTC Sets
    • 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 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 wiring at the PCM, the transmission 20-way connector, and the TFT sensor 2-way connector 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
    • 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 Description

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

  1. This step ensures that the transmission fluid is at the proper level.

    2.

  2. This step verifies DTC P0712 by indicating a short to ground. If the scan tool does not display a voltage value equal to or less than 0.08 volts, then the DTC is intermittent.

    3.

  3. This step isolates the transmission. If the scan tool displays a voltage greater than 4.8 volts, then the engine wiring harness is good.

    4.

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

DTC P0712 TFT Sensor Circuit Low Input

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

2

Was the Transmission Fluid Checking Procedure performed?

--

Go to Step 3

Go to Transmission Fluid Check

3

  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 TFT Sensor on the scan tool.

Does the scan tool display TFT sensor voltage equal to, or less than, the specified value?

0.08V

Go to Step 4

Go to Diagnostic Aids

4

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

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

4.8V

Go to Step 6

Go to Step 5

5

Inspect circuit 1227 of the engine wiring harness for a short to ground.

Refer to General Electrical Diagnosis in Wiring Systems.

Was the condition found?

--

Go to Step 9

Go to Step 12

6

  1. Install 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.

Is the resistance within the range specified for the given transmission temperatures?

20°C (68°F) 3088-3942 ohms

80°C (176°F) 159-198 ohms

Go to Step 7

Go to Step 8

7

Measure the resistance between terminal M and a good ground on the transmission case.

Is the resistance less than the specified value?

100 ohms

Go to Step 10

Go to Diagnostic Aids

8
  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 .

Is the resistance less than the specified value?

100 ohms

Go to Step 10

Go to Step 11

9

Repair the wiring as necessary.

Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 13

--

10

Replace the automatic transmission wiring harness.

Refer to Unit Repair.

Is the replacement complete?

--

Go to Step 13

--

11

Replace the TFT sensor.

Refer to Unit Repair.

Is the replacement complete?

--

Go to Step 13

--

12

Replace the PCM.

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

Is the replacement complete?

--

Go to Step 13

--

13

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. 3.1. Start the engine.
    3.2. While the engine is idling, monitor the TFT sensor volts.
    3.3. Ensure the voltage is greater than 0.08 volts for more than 5 seconds.
  4. Select Specific DTC. Enter DTC P0712.

Has the test run and passed?

--

System OK

Go to Step 1