Circuit Description
The Automatic Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor whose resistance value changes based on temperature. The Powertrain Control Module (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).
If 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
| • | The PCM does not illuminate the Malfunction Indicator Lamp (MIL). |
| • | 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 115°C (239°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 110°C (230°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 ignition ON. |
| • | If 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 27°C (81°F) at ignition ON. If the intake air temperature is greater than 27°C (81°F) at ignition ON, the transmission fluid default temperature equals ECT+10°C. |
| • | 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). |
| • | DTC P0712 is stored in the PCM history. |
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 problems: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| - | Moisture intrusion |
| • | 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 table.
-
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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This step tests the Automatic Transmission Fluid Temperature circuit 1227 inside of the transmission for a short to ground.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | 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. Using the Clear Info function will erase the stored Failur Records from the PCM. 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 | |||||||||
5 | 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? | -- | ||||||||
Is the resistance greater than the specified value? | 100 ohms | |||||||||
7 | Inspect the Automatic Transmission Wiring Harness circuit 1227 for a short to ground. Refer to Electrical Diagnosis, Section 8. Did you find the condition? | -- | ||||||||
8 | Replace the Automatic Transmission Wiring Harness. Refer to Automatic Transmission Wiring Harness Replacement. Is the replacement complete? | -- | -- | |||||||
9 | Replace the Automatic Transmission Fluid Temperature sensor. Refer to TFT Sensor Replacement, in On-Vehicle Service. Is the replacement complete? | -- | -- | |||||||
10 | Replace the PCM. Refer to PCM Replacement/Programming Section 6. Is the replacement complete? | -- | -- | |||||||
11 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
