Circuit Description
The transmission fluid temperature (TFT) sensor is part of the pressure switch manifold (PSM) assembly, and is located in the transmission oil pan. The TFT sensor is a thermistor, which changes value based on the temperature of the transmission fluid. The transmission control module (TCM) supplies a 5-volt reference voltage signal to the TFT sensor and measures the voltage drop in the circuit. When the transmission 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. The TCM uses this information to control shift quality and torque converter clutch (TCC) apply.
DTC P0712 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit - Low Input
Conditions for Running the DTC
| • | DTC P0711 and P0713 are not active. |
| • | The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts. |
| • | Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds. |
| • | The engine has been running for 20 seconds with a coolant temperature above 20°C (68°F). |
Conditions for Setting the DTC
DTC P0712 sets when the TCM detects a voltage of less than 313m volts for 2.5 seconds.
Action Taken When the DTC Sets
| • | The TCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. |
| • | The TCM uses a TFT default value. |
| • | The TCM freezes shift adapts. |
| • | The TCM stores this information as Failure Records. |
| • | The TCM stores DTC P0712 in TCM history. |
| • | The TCM inhibits TCC engagement. |
Conditions for Clearing the DTC
A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.
Diagnostic Aids
| • | Inspect the wiring for poor electrical connections at the TCM. Inspect 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 |
| • | When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. |
| • | You may have to drive the vehicle in order to experience a condition. |
| • | A short to ground allows DTC P0712 to set. |
| • | DTC P0218 may set after DTC P0712 has set. Follow the diagnostic table for DTC P0712 before proceeding to the diagnostics for DTC P0218. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests 5-volt reference.
-
This step tests the TFT sensor and internal wiring harness.
-
This step tests the resistance of the TFT sensor.
Step | Action | Value | Yes | No |
|---|---|---|---|---|
Schematic Reference: Automatic Transmission Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 | Measure the transmission fluid level. Refer to Transmission Fluid Check . Is the transmission fluid level correct? | -- | Go to Step 3 | Go to Transmission Fluid Check |
3 |
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Is the TFT reading at or below the specified value? | -36°C (-32°F) | Go to Step 4 | Go to Diagnostic Aids |
Is voltage within the specified value? | 5 V | Go to Step 5 | Go to Step 11 | |
5 |
Is the resistance within the specified value? | 3,490 ohms @ 20°C (68°F) 177.9 ohms @ 100°C (212°F) | Go to Diagnostic Aids | Go to Step 6 |
Is the resistance within the specified value? | 3,490 ohms @ 20°C (68°F) 177.9 ohms @ 100°C (212°F) | Go to Step 8 | Go to Step 7 | |
Is resistance within the specified value? | 3,490 ohms @ 20°C (68°F) 177.9 ohms @ 100°C (212°F) | Go to Step 9 | Go to Step 10 | |
8 | Test the PSM circuit between the TCM and AT inline 20-way connector for a short to ground condition. Refer to Testing for Short to Ground . Did you find and correct the condition? | -- | Go to Step 12 | -- |
9 | Replace the automatic transmission internal harness. Refer to Wiring Harness Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
10 | Replace the PSM. Refer to Pressure Switch Manifold Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 |
Important: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM. Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | -- |
12 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 13 | Go to Step 2 |
13 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
