Circuit Description
The automatic transmission fluid temperature (TFT) sensor is a thermistor. The TFT sensor is part of the automatic transmission fluid pressure (TFP) manual valve position switch. The PCM supplies a 5-volt reference signal to the sensor. When the transmission fluid is cold, the sensor resistance is high and the PCM senses a high signal voltage. As the transmission fluid warms, the sensor resistance lowers and the PCM senses lower voltage. The PCM uses the TFT reading in order to control the torque converter clutch (TCC), line pressure adjustments, and temperature compensated shifts.
When the PCM detects a continuous short to ground in the TFT circuit or the TFT sensor, then DTC P0712 sets. DTC P0712 is a type C DTC.
Conditions for Running the DTC
| • | The ignition switch is in the ON position. |
| • | The system voltage is 8-18 volts. |
Conditions for Setting the DTC
The TFT voltage is less than 0.33 volts for 10 seconds.
Action Taken When the DTC Sets
| • | The PCM does not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM freezes shift adapts from being updated. |
| • | The PCM calculates a default transmission fluid temperature based on engine coolant temperature, intake manifold air temperature, and engine run time. |
| • | 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 can clear the DTC. |
| • | The PCM clears the DTC from PCM history if the vehicle completes 40 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/or the ignition switch is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | Inspect the connections at the PCM, the TFP manual valve position switch 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.
-
This step tests the PCMs ability to detect an open circuit.
-
This step tests the TFT sensor for correct resistance.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain Diagnostic System Check? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check (2.2L) or Powertrain On Board Diagnostic (OBD) System Check (2.4L) | |||||
2 |
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 PCM. Does the Scan Tool display a TFT sensor voltage greater than the specified value? | 0.33 V | Go to Diagnostic Aids | |||||
Does the Scan Tool display a TFT sensor voltage greater than the specified value? | 4.92 V | |||||||
4 | Test the signal circuit (CKT 1227) of the TFT sensor for a short to ground between the PCM connector C1 and the AT inline 20-way connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||
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) 3106-3923 ohms 100°C (212°F) 164-190 ohms | |||||||
6 | Measure the resistance between terminal L of the J 44152 and a good ground. Refer to Automatic Transmission Inline Harness Connector End View . Is the resistance less than the specified value? | 1000 ohms | Go to Diagnostic Aids | |||||
7 |
Refer to Automatic Transmission Inline Harness Connector End View . Is the resistance less than the specified value? | 1000 ohms | ||||||
8 | Replace the TFP manual valve position switch. Refer to the Pressure Switch Assembly Replacement. Did you complete the replacement? | -- | -- | |||||
9 | Replace the automatic transmission wiring harness. Refer to Transmission Overhaul in the 4T40-E/4T45-E section of the Transmission Unit Repair Manual. Did you complete the replacement? | -- | -- | |||||
10 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming (2.2L) or Powertrain Control Module Replacement/Programming (2.4L) in Engine Controls. Did you complete the replacement? | -- | -- | |||||
11 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | System OK |
