Circuit Description
The automatic transmission fluid temperature (TFT) sensor is part of the 4L30-E automatic transmission wiring harness assembly. The TFT sensor is a resistor, or thermistor, which changes value based on temperature. The sensor has a negative-temperature coefficient. This means that as the temperature increases, the resistance decreases, and as the temperature decreases, the resistance increases. The transmission control module (TCM) supplies a 5-volt reference signal to the sensor on circuit FP722 and measures the voltage drop in the circuit. When the transmission fluid is cold, the sensor resistance is high and the TCM detects high signal voltage. As the fluid temperature warms to a normal operating temperature, the resistance becomes less and the signal voltage decreases.
If the TCM detects an open or a short to ground in the TFT sensor or signal circuit, then DTC P0712 sets. DTC P0712 is a type C DTC.
Condition For Running The DTC
The ignition switch is in the RUN position.
Conditions For Setting The DTC
| • | The TFT is less than 98 mV. |
| • | Condition present for 20 seconds. |
Action Taken When the DTC Sets
| • | Early production - The TCM illuminates the service transmission lamp (STL). |
| • | Late production - The TCM flashes the Sport Mode Lamp. |
| • | The ECM records the operating conditions in the Failure Records at the time of the request from the TCM. |
| • | The TCM memory stores the DTC at the time of the first failure. |
| • | The transmission temperature defaults to 130°C (266°F). |
| • | The TCM will freeze shift adapts. |
Conditions For Clearing the MIL/DTC
| • | Early production - The TCM turns off the STL as soon as the fault is no longer present. |
| • | Late production - The TCM stops flashing the sport mode lamp as soon as the fault is no longer present. |
| • | A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic. |
| • | The scan tool clears the MIL/DTC. |
| • | The TCM cancels the DTC default mode actions when the fault no longer exists and the ignition switch is Off long enough in order to power down the TCM. |
Diagnostic Aids
Vehicles equipped with Fuel Cap Lamps utilize the Sport Mode lamp to indicate a transmission malfunction. In these vehicles, the Sport Mode Lamp flashes at 200 millisecond intervals when the TCM commands the lamp ON.
Vehicles not equipped with Fuel Cap Lamps are equipped with a dedicated Service Transmission Lamp (STL) on the Instrument Panel Cluster (IPC). The STL illuminates steadily when the TCM commands the lamp ON.
Use the J 35616-A connector test adapter kit for any test that requires probing the TCM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.
Check for the following conditions:
| • | Poor connections at the TCM or at the component. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| Refer to General Electrical Diagnosis in Wiring Systems for proper procedure. |
| • | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving any related connectors and any wiring harnesses. A change in the display may help to locate the fault. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the TCMs ability to detect an open circuit. If the TCM recognizes the open, this eliminates the TCM and the wiring up to the transmission connector from having the fault. The fault must be internal to the transmission.
-
This step inspects for the two TFT circuits for being shorted together.
-
Since the TFT is an integral part of the transmission wiring, the entire harness must be replaced.
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||||
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 ECM/TCM. Does the Scan Tool display a TFT Sensor voltage less than the specified value? | 0.09 volts | Go to Diagnostic Aids | |||||||||||
Does the Scan Tool display a TFT sensor voltage greater than the specified value? | 4.35 volts | |||||||||||||
4 | Using the J 39200 digital multimeter (DMM) and the J 35616-A connector test adapter kit, measure terminal F voltage on the TCM side of the transmission harness. Is the voltage within the specified value? | 5.3-4.7 volts | Go to Diagnostic Aids | |||||||||||
Check circuits FP 722 and XU 716 for being short together Was the condition found? | -- | |||||||||||||
6 | Check circuit XU 716 for a short to ground. Was the condition found? | -- | ||||||||||||
7 | Check the transmission internal wiring circuit FP 722 (green wire) or the TFT for being shorted to:
Was the condition found? | -- | -- | |||||||||||
8 | Make the necessary wiring repairs. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||||
Replace the main case harness assembly. Refer to Control Valve Body . Is the repair complete? | -- | -- | ||||||||||||
10 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the repair complete? | -- | -- | |||||||||||
11 | Perform the following procedure in order to verify the repair:
Does the Scan Tool display a TFT Sensor voltage greater than the specified value? | 0.15 volts | System OK |
