Circuit Description
The automatic transmission fluid temperature (TFT) sensor is part of the 4L30-E automatic transmission internal wiring harness assembly. The TFT sensor is a thermistor, or a resistor that changes value when the temperature changes. 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 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 increases, the resistance decreases, which pulls down the signal voltage.
If the TCM detects 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 is ON.
Conditions For Setting The DTC
The TFT sensor voltage is less than 98 mV. for more than 20 seconds.
Action Taken When the DTC Sets
| • | The TCM flashes the sport mode lamp. |
| • | The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM records this information as Failure Records. |
| • | The TCM stores DTC P0712 in TCM history. |
| • | The TCM uses a default temperature value of 130°C (266°F). |
| • | The TCM freezes shift adapts from being updated. |
Conditions For Clearing the MIL/DTC
| • | The TCM stops flashing the sport mode lamp as soon as the fault is no longer present. |
| • | A scan tool can clear the DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring. |
| • | The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM. |
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
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This step tests the ability of the TCM 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.
-
Since the TFT is an integral part of the transmission wiring, the entire harness must be replaced.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission ? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission | |
2 |
Important: Record the Failure Records before clearing the DTCs. Using the Clear Info function erases the Failure Records from the ECM and the TCM. Does the scan tool indicate that the TFT sensor signal voltage is less than the specified value? | 0.09 V | Go to Intermittent Conditions in Engine Controls | |
Does the scan tool indicate that the TFT sensor voltage is greater than the specified value? | 4.35 V | |||
4 |
Caution: When you are performing service on or near the SIR components or the SIR wiring, you must disable the SIR system. Refer to Disabling the SIR System. Failure to follow the correct procedure could cause air bag deployment, personal injury, or unnecessary SIR system repairs. Test the Transmission Oil Temperature Signal circuit (CKT FP722) for a short to ground. Refer to Testing for Short to Ground in Wiring Systems. Did you find and correct the condition? | -- | ||
Replace the AT main case wiring harness assembly. Refer to Control Valve Body . Is the action complete? | -- | -- | ||
6 |
Caution: When you are performing service on or near the SIR components or the SIR wiring, you must disable the SIR system. Refer to Disabling the SIR System. Failure to follow the correct procedure could cause air bag deployment, personal injury, or unnecessary SIR system repairs. Replace the TCM. Refer to Transmission Control Module Replacement . Is the action complete? | -- | -- | |
7 | Perform the following procedure in order to verify the repair:
Does the scan tool display a voltage greater than the specified value? | 0.15 V | System OK |
