DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input 3.1L Vin M Only
Circuit Description
The Automatic Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor. When the transmission fluid is cold, the sensor resistance is high. As the transmission fluid warms, the sensor resistance decreases. The TFT range is -40 to +150°C (-40 to +302°F).
The PCM provides a 5 volt reference through a fixed series resistor to the TFT circuit, and monitors the voltage after the resistor, as the voltage drop (signal) across the circuit.
When the PCM detects a voltage input of less than 0.20 V in the TFT Sensor circuit, indicating a short to ground or short together, then DTC P0712 sets. DTC P0712 is a type D DTC.
Conditions for Setting the DTC
| • | System voltage is 10-16 volts. |
| • | The ignition is ON. |
| • | The PCM detects a TFT sensor voltage of 0.20 volts or less for 10 seconds. |
Action Taken When the DTC Sets
| • | The PCM does not illuminate the Malfunction Indicator Lamp (MIL). |
| • | The PCM calculates a transmission fluid default temperature as follows: |
| • | If any engine coolant temperature sensor codes are set, the PCM substitutes a transmission fluid temperature default value of 131°C (268°F). |
| • | If the engine coolant temperature is greater than 115°C (239°F), the PCM substitutes a transmission fluid temperature default value of 131°C (268°F). |
| • | If the engine run time is less than 3 minutes, the PCM substitutes the intake air temperature for the transmission fluid temperature value at startup except if any inlet air temperature codes are set, the PCM sets default temperature to 0°C (32°F). |
| • | If engine run time is greater than 3 minutes and the engine coolant temperature is 45-115°C (113-239°F), the transmission fluid default temperature equals ECT-10°C when the intake air temperature is less than 0°C (32°F) at startup. If the intake air temperature is greater than 28°C (82°F) at startup, the transmission fluid default temperature equals ECT+10°C. If the intake air temperature (IAT) is 0-28°C (32-82°F) or any IAT DTC codes are set then transmission fluid default temperature is set to coolant temperature. |
| • | If the engine run time is greater than 3 minutes and the engine coolant temperature is less than 45°C (113°F), the PCM substitutes a transmission fluid temperature default value of 12°C (54°F). |
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 at the PCM, the transmission connector and all other circuit connecting points 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 or open condition, massage the wiring harness while watching the test equipment for a change. |
| • | Inspect the transmission harness for a short to ground. Inspect the engine harness for a short to ground. |
| • | Inspect the transmission cooling system for blockage or other restrictions. |
| • | Refer to Temperature vs Resistance . |
| • | Test the TFT Sensor at various temperature levels in order to evaluate the possibility of a skewed (mis-scaled) sensor. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
A scan tool display of 145°C (293°F) or more indicates that this DTC is current.
-
This action isolates the fault between the transmission harness and the engine harness.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||
2 | Have you performed the Transmission Fluid Checking Procedure? | -- | Go to Transmission Fluid Check | |||||
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. Using the Clear Info function will erase the stored Freeze Frame and Failure Records from the PCM. Does the scan tool display a TFT sensor voltage less than the specified value? | 0.20 volts | Go to Diagnostic Aids | ||||||
Does the scan tool display a TFT sensor voltage greater than the specified value? | 4.92 volts | |||||||
5 | Inspect circuit 1227 of the engine harness for a short to ground. Refer to General Electrical Diagnosis in Wiring Systems. Was a condition found and corrected? | -- | ||||||
6 |
Does the DMM display a resistance greater than that specified? | 100K ohms | ||||||
7 |
Is the resistance below the specified value? | 100K ohms | ||||||
8 | Replace the Automatic Transmission Wiring Harness. Refer to Solenoids and Wiring Harness Replacement. Is the replacement complete? | -- | -- | |||||
9 | Replace the TFT Sensor. Refer to Fluid Temperature Sensor Replacement. Is the replacement complete? | -- | -- | |||||
10 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls. Is the replacement complete? | -- | -- | |||||
11 | Perform the following procedure, to verify your repair:
Has the test run and passed? | -- | System OK |
