Comprehensive Diagnostic Guide for P0713

Transmission Fluid Temperature Sensor A Circuit High Input

Overview

• Definition (standard code context): P0713 is a powertrain diagnostic trouble code indicating a high input condition on the Transmission Fluid Temperature Sensor (TFTS) circuit, commonly referred to in vendor definitions as In practice, the PCM detects a voltage/readout in the TFTS circuit that it interprets as an abnormally high signal. This code is categorized under OBD-II powertrain codes.
• Sensor context: Transmission fluid temperature sensors monitor the temperature of the transmission fluid, and the PCM uses that data to manage shift timing, line pressure, and, in some cases, torque-converter behavior. A circuit high input can be caused by a faulty sensor, wiring/connectors, or PCM/ECU issues.

Symptoms

• Check Engine Light (MIL) illuminated.
• Transmission shifting anomalies such as harsh or delayed shifts, shifting into limp/limited mode, or abnormal shift timing.
• Possible reduction in fuel economy or hesitation when shifting gears.
• In some vehicles, the PCM may adapt to a faulty reading and cause other transmission-related drivability concerns.

Note: Symptom severity and manifestation vary by make, model, and whether the vehicle is in a diagnostic "limp" or normal operating state.

Probable Causes

• Most probable: Faulty transmission fluid temperature sensor A or its circuit
  • Reason: The circuit high input is most directly caused by a defective TFTS, a sensor with an internally failed circuit, or a sensor that has lost its reference/ground path. This is the single most common cause for P0713 in many makes/models.
  • Estimated probability (field experience): 40-60%
• Wiring/connector issues in the TFTS circuit
  • Reason: Damaged, corroded, pin-stretched, or moisture-absorbed connectors and wiring harness damage near the sensor or along the harness can create a high (or erratic) input signal due to poor contact or short to supply.
  • Estimated probability: 20-35%
• PCM/ECU input, grounding, or software/firmware considerations
  • Reason: A faulty PCM input channel, a fault in the reference voltage, or a software/firmware fault can misinterpret legitimate sensor signals as high input. Rare but possible, especially after module updates or resections.
  • Estimated probability: 5-15%
• Transmission fluid or environmental factors causing sensor misread
  • Reason: If the sensor is exposed to contamination, corrosion, or is sitting in a faulty fluid path, readings can drift; however, most of these would typically present as sensor/wiring faults rather than a clean "high input" signal. This is a secondary consideration.
  • Estimated probability: 5-10%
• Other circuit anomalies (grounding issues, parasitic leakage)
  • Reason: Intermittent grounding or electrical noise can occasionally masquerade as a high input on the TFTS circuit.
  • Estimated probability: 5-10%

Important Notes

• establish the general context of OBD-II trouble codes (Diagnostic Trouble Codes, Powertrain Codes) and the concept that these codes reflect abnormal sensor data or circuit conditions in the vehicle's powertrain. They do not provide vehicle-specific P0713 thresholds or exact test values.
• An Open Source GitHub entry defines the code as i.e., a high input on Transmission Fluid Temperature Sensor A. This aligns with the general definition that P0713 relates to a high-input condition in the TFTS circuit.
• No corresponding NHTSA complaint dataset is provided ; the probability estimates reflect ASE-field experience alongside general diagnostic practice, not a formal complaints analysis from NHTSA data.

Diagnostic Approach

1) Establish baseline and verify the DTC

• Confirm the P0713 code in the vehicle's scan tool and note any related codes (for example, P0713 may appear with other TFTS or transmission-related codes). Retrieve freeze-frame data and recorded live data to establish the temperature range the PCM saw when the fault triggered.

2) Visual inspection of TFTS circuit and sensor

• Inspect the TFTS connector and its wiring for obvious damage, corrosion, moisture, or signs of heat damage.
• Check for bent or pushed pins, loose connectors, or signs of previous repair in the harness near the sensor.
• Look for wiring harness wear where it travels near moving components or along the transmission.

3) Sensor data validation (live data and basic electrical tests)

• With key on, engine off (and later with engine running if safe), observe TFTS voltage or commanded data on the scan tool. Note if the signal is presented as abnormally high or unstable.
• Backprobe the TFTS signal line (careful not to damage the pin) to measure actual circuit voltage and compare to known good ranges for the vehicle. If a reference voltage is present (commonly 5V or analogous), check that it is not shorted to supply or ground.
• Check the ground path for the TFTS circuit. A poor ground can produce erroneous high readings or fluctuating signals.

4) Sensor resistance and functional test

• If possible, test the TFTS resistance at the sensor terminals across a known temperature range (or compare to a service manual's resistance vs. temperature spec). A sensor that is out of spec or subject to internal failure will show improper resistance changes with temperature.
• If the resistance vs. temperature is not within spec, replace the TFTS.

5) Circuit integrity and harness testing

• Perform continuity tests along the TFTS wiring harness to identify opens or shorts to power or ground.
• Inspect for shorts to adjacent wires, contact with hot surfaces or water intrusion into the harness or connector.
• If water intrusion or corrosion is found, clean/repair or replace the affected wiring/connectors.

6) PCM/ECU considerations

• If sensor and wiring tests pass yet the code persists, consider PCM fault or software issue. Check for any available manufacturer service bulletins or software updates that address TFTS input behavior.
• In some cases, re-flashing or updating the PCM/TCU software (as per the vehicle's service bulletin) can resolve spurious high-input readings.

7) Fluid and environmental checks

• Verify transmission fluid level and condition. While P0713 is a circuit fault, extremely low or degraded fluid can affect sensor readings indirectly via environmental conditions and sensor exposure. Correct any fluid level/condition issues if found.

8) Verdict and repair path

• If TFTS or its wiring is defective: replace TFTS, repair harness/connectors, then re-test to ensure P0713 no longer sets.
• If wiring or connector issues are found: repair/replace wiring harness or connectors, retest.
• If PCM/firmware is implicated: perform recommended service bulletin steps, software update, or PCM replacement if required.
• After any repair, clear codes, run a drive cycle, and verify no reoccurrence of P0713 under normal operating conditions.

Recommended tests and verification prompts

• After repair or replacement, perform a drive cycle that exercises transmission temperatures (e.g., city driving then stop-and-go and highway cruising) to ensure the TFTS reads within expected ranges across the operating temperature spectrum.
• Confirm other TF-related codes are clear and review live data to ensure the transmission control strategy remains consistent with expected behavior.
• If the vehicle allows, monitor actual fluid temperature versus ambient temperature to ensure readings track plausibly (and that no new TFTS faults appear).

Safety Considerations

• Work on the vehicle with the engine off and cooled when inspecting sensors near the transmission; some components can get very hot in operation.
• Use appropriate personal protective equipment and follow standard electrical safety practices when probing live circuits.
• If you suspect multiple implicated circuits or a PCM fault, consult the manufacturer service documentation before performing aggressive electrical tests or replacements.

Summary

• P0713 points to a high input condition on the Transmission Fluid Temperature Sensor A circuit. The most common cause is a faulty TFTS or its wiring, but harness/connectors, PCM issues, and environmental factors can contribute. A structured diagnostic flow-visual inspection, electrical testing of the sensor circuit, resistance checks, and PCM considerations-will isolate the fault. Replacing the faulty component and validating with a drive cycle generally resolves the code.

References (contextual)

• Open Source GitHub Definition: (Transmission Fluid Temperature Sensor A High Input) - aligns with P0713 definition for TFTS A Circuit High Input

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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