For 1990-2009 cars
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 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 D DTC.

### Conditions for Setting the DTC

• | The system voltage is 9-16 volts.

• | The ignition is ON.

• | The PCM detects a TFT sensor voltage of 0.200 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 disables shift adapts.

• | The default TFT will be determined through the following calculations:

- | If the Engine Run Time is less than 3 minutes and:

• | Intake Air Temperature (IAT) DTC P0112, P0113, P1111 or P1112 is set, then the default TFT is 0°C (32°F).

• | No IAT DTC is set, then the default TFT is set to the IAT saved at start up.

- | If the Engine Run Time is greater than 3 minutes, and the Engine Coolant Temperature (ECT) DTC P0117, P0118, P1114 or P1115 is set, then the default TFT is 131°C (268°F).

- | If the Engine Run Time is greater than 3 minutes, no ECT DTC is set and:

• | The ECT is less than 45°C (113°F), then the default TFT is 12°C (54°F).

• | The ECT is greater than 115°C (239°F), then the default TFT is 131°C (268°F).

• | The ECT is 45-115°C (113-239°F) and:

- | The IAT DTC P0112, P0113, P1111 or P1112 is set, then the default TFT is set to equal the ECT.

- | The IAT at start up is less than 0°C (32°F), then the default TFT is set to ECT minus 10°C (18°F).

- | The IAT at start up is greater than 28°C (82°F), then the default TFT is set to ECT plus 10°C (18°F).

- | The IAT at start up is 0-28°C (32-82°F), then the default TFT is set to equal ECT.

### Conditions for Clearing the DTC

• | A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.

• | The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

### Diagnostic Aids

• | Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following conditions:

- | A bent terminal

- | A backed out terminal

- | A damaged terminal

- | Poor 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. This step tests the TFT sensor for correct resistance.

#### DTC P0712 Transmission Fluid Temperature 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 in Engine Controls
2 |

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

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 OFF.
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 General Electrical Diagnosis in Wiring Systems. Was the condition found? | -- | Go to Step 8 | Go to Step 11
5 |

1. Install the J 39775 Jumper Harness to the transmission side of the 20-way connector.
2. Using the 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? | 1,000 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?

1,000 ohms

Go to Step 10

Go to Step 9

8 | Repair the wiring as necessary. 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. 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:

• | 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