Circuit Description
The automatic transmission fluid temperature (TFT) sensor is part of the 4L80-E automatic transmission (A/T) wiring harness assembly. The TFT sensor is a resistor, or thermistor, which changes value based on temperature. 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 powertrain control module (PCM) supplies a 5-volt reference signal to the sensor on CKT 1227 and measures the voltage drop in the circuit. When the transmission fluid is cold, the sensor resistance is high and the PCM detects high signal voltage. As the fluid temperature warms to a normal operating temperature, the resistance becomes less and the signal voltage decreases. The PCM uses this information to control shift quality and torque converter clutch apply.
If the PCM detects a continuous open or short to the power in the TFT signal circuit or the TFT sensor, then DTC P0713 sets. DTC P0713 is a type D DTC.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The TFT sensor indicates a voltage greater than 4.94 volts. |
| • | All conditions met for 400 seconds. |
Action Taken When the DTC Sets
| • | The PCM does not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM commands increased line pressure. |
| • | The PCM freezes shift adapts. |
| • | The PCM determines a TFT default transmission temperature (TFT) using the following matrix: |
| - | If the engine run time is less than 60 seconds then default TFT equals the intake air temperature (IAT), plus 5 degrees. |
| - | If the engine coolant temperature (ECT) is less than 85°C (185°F) then default TFT equals IAT plus 10 degrees. |
| - | If the ECT is 85°-110°C (185°-230°F) then default TFT equals ECT plus 10 degrees. |
| - | If the ECT is greater than 110°C (230°F) then default TFT is set to 140°C (284°F) and transmission shift pattern is in hot mode. |
| - | If ECT and TFT DTCs are both set then default TFT is 140°C (284°F). |
| • | The PCM stores DTC P0713 in PCM history. |
Conditions for Clearing the DTC
| • | A scan tool clears the DTC from PCM history. |
| • | The PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission-related diagnostic fault occurring. |
| • | The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | Inspect the harness for a faulty connection or an open in CKT 1227. |
| • | Inspect the wiring at the PCM, the transmission connector and all other circuit connecting points for the following conditions: |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Reduced terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| - | Moisture intrusion |
| - | Corrosion |
| • | High voltage (B+) in CKT 1227 may also damage the TFT sensor. |
| • | When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. |
| • | The scan tool displays the transmission fluid temperature (TFT) in degrees. After the transmission operates, the temperature rises steadily to about 100°C (212°F). The temperature then stabilizes. |
| • | Test the TFT sensor at the various temperatures in order to evaluate the possibility of a skewed (mis-scaled) sensor. Use the Temperature vs Resistance table. A skewed sensor may cause firm shifts or TCC complaints. |
| • | First diagnose and clear any engine DTCs or TP sensor codes that are present. Then inspect for any transmission DTCs that may have reset. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for higher than normal circuit voltage which may also damage the TFT sensor.
-
This step simulates a TFT sensor DTC P0712. If the PCM recognizes the low signal voltage (high temperature), and the scan tool displays 146°C (295°F) or greater, the PCM and the wiring are OK.
-
This step verifies a problem in the TFT sensor circuit inside the transmission.
-
This step inspects the TFT sensor and the automatic transmission wiring harness assembly (A/T wiring harness assembly) for an open. CKT 470 becomes CKT 452 inside the transmission.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 | Perform the Transmission Fluid Checking Procedure. Refer to Transmission Fluid Check . Was the fluid checking procedure performed? | -- | -- | |
3 |
Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM. Does the scan tool display a TFT sensor signal voltage greater than the specified value? | 4.92 volts | Go to Diagnostic Aids | |
|
Important: Refer to Test Description for information about step 4. Does the scan tool display a TFT voltage greater than the specified value? | 5.1 volts | |||
5 |
Refer to Electronic Component Description . Is the voltage within the specified range? | 4.9-5.0 Volts | ||
Is the scan tool TFT sensor signal voltage less than the specified value? | 0.2 volts | |||
Refer to Electronic Component Description . Is the resistance within the specified range? | 16kΩ at - 10°C (14°F) to 133Ω at 110°C (230°F) | Go to Diagnostic Aids | ||
Refer to Automatic Transmission Fluid and Filter Replacement. Refer to General Electrical Diagnosis in Wiring Systems. Was an open condition found? | -- | |||
9 | Replace the A/T wiring harness assembly. Refer to Wiring Harness Replacement. Is the replacement complete? | -- | -- | |
10 | Inspect CKT 1227 (YEL/BLK) for high resistance or an open. Refer to General Electrical Diagnosis in Wiring Systems. Was the condition found? | -- | ||
11 | Inspect CKT 1227 (YEL/BLK) for a short to voltage B+. Was the condition found? | -- | ||
12 | Inspect CKT 407 (BLK) for an open. Refer to General Electrical Diagnosis in Wiring Systems. Was the condition found? | -- | ||
13 | Inspect the PCM for faulty or intermittent connections. Was the condition found? | -- | ||
14 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls. Is the replacement complete? | -- | -- | |
15 | Replace the TFT sensor. Refer to Wiring Harness Replacement. Is the replacement complete? | -- | -- | |
16 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | System OK |
