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 +305°F).
When 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 PCM detects a TFT of 148°C (298°F) or greater (0.08 volts or less) for 5 seconds.
Action Taken When the DTC Sets
| • | If any engine coolant temperature sensor codes set, the PCM substitutes a transmission fluid temperature default value of 132°C (269°F). |
| • | If the engine coolant temperature is greater than 110°C (230°F), the PCM substitutes a transmission fluid temperature default value of 132°C (269°F). This enables Transmission Hot Mode. The transmission remains in Hot Mode until the engine coolant temperature drops below 105°C (221°F). |
| • | If the engine run time is less than 5 minutes, the PCM substitutes the intake air temperature for the transmission fluid temperature value at ignition ON. |
| • | If the engine coolant temperature is 70-110°C (158-230°F), the transmission fluid default temperature equals ECT-10°C when the intake air temperature is less than 80°C (176°F) at ignition ON. If the intake air temperature is greater than 80°C (176°F) at ignition ON, the transmission fluid default temperature equals ECT+10°C. |
| • | If none of the above conditions exist, the PCM substitutes a transmission fluid temperature default value of 80°C (176°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 for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Inspect the wiring for poor electrical connections at the Automatic Transmission Fluid Temperature sensor connector. Look for the following conditions: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| • | 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 Description
The numbers below refer to the step numbers on the diagnostic chart.
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This Step ensures that you perform the Powertrain On-Board Diagnostic System Check.
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This Step ensures that the transmission fluid is at the proper level.
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This Step verifies DTC P0712 by indicating a short to ground. If the scan tool does not display a voltage value equal to or less than 0.08 volts, then the DTC is intermittent.
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This Step isolates the transmission. If the scan tool displays a voltage greater than 4.8 volts, then the Engine Wiring Harness is good.
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If the scan tool display remains at a value equal to or less than 0.08 volts, inspect circuit 1227 of the Engine Wiring Harness for a short to ground.
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This Step tests the Automatic Transmission Fluid Temperature circuit 1227 inside of the transmission for a short to ground. Use the J 35616-A Test Connector Adapter Kit, so as not to damage the terminals.
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This Step assumes that the ohmmeter display is less than 100 ohms. Inspect the Automatic Transmission Wiring Harness circuit 1227 for a short to ground. If you find a short to ground, replace the Automatic Transmission Wiring Harness
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This Step replaces the Automatic Transmission Fluid Temperature sensor after you have inspected circuit 1227 and found no short to ground.
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This Step replaces the PCM only after you have inspected the circuitry and component.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | ||||||||
Has the transmission fluid checking procedure been performed? | -- | Go to Transmission Fluid Check | ||||||||
Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records for reference. The Clear Info function will erase the data. Does the scan tool display an Automatic Transmission Fluid Temperature equal to, or less than, the specified value? | 0.08V | Go to Diagnostic Aids | ||||||||
Does the scan tool display an Automatic Transmission Fluid Temperature voltage greater than the specified value? | 4.8V | |||||||||
Inspect circuit 1227 of the Engine Wiring Harness for a short to ground. Refer to Electrical Diagnosis, Section 8. Did you find and correct the condition? | -- | |||||||||
Does the ohmmeter display a resistance greater than the specified value? | 100ohms | |||||||||
Inspect circuit 1227 for a short to ground. Refer to Electrical Diagnosis, Section 8. Did you find and correct the condition? | -- | |||||||||
Replace the Automatic Transmission Fluid Temperature sensor. Refer to TFT Sensor Replacement. Is the replacement complete? | -- | -- | ||||||||
Replace the PCM. Refer to PCM Replacement/Programming Section 6. Is the replacement complete? | -- | -- | ||||||||
10 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
