P0707 Error Code

Issue Description

The P0707 "Transmission Range Sensor 'A' Circuit Low Input" error code in Ford vehicles refers to a low voltage signal detected from the Transmission Range Sensor (TRS) or gear position sensor. The TRS informs the powertrain control module (PCM) about the gear selection (Park, Reverse, Neutral, Drive). A "low input" means that the signal voltage from the sensor is lower than the acceptable range, causing the PCM to detect an error.

When this error occurs, it typically points to an issue with the sensor or the wiring that transmits its signal to the PCM, leading to transmission-related problems that affect drivability.

Ford P0707 Error Code

Symptoms

When the P0707 code is triggered, drivers may experience a range of symptoms, which are mostly related to transmission issues. Some of the common signs include:

  • Inability to start the vehicle: The engine may not crank if the PCM cannot confirm the vehicle is in Park or Neutral.
  • Erratic shifting: The transmission may behave unpredictably, including failing to shift properly between gears.
  • Stuck in "limp" mode: The vehicle might limit itself to lower gears (usually second or third) to protect the transmission.
  • Illuminated Check Engine Light (CEL): The CEL will turn on, often accompanied by other transmission warning lights.
  • Incorrect Gear Display: The gear selector display may not match the actual gear the vehicle is in, confusing the driver.

Causes

Several factors can lead to the P0707 error, typically revolving around issues with the transmission range sensor and its related circuitry. The most common causes include:

  • Faulty Transmission Range Sensor (TRS): A malfunctioning TRS is the most likely cause. The sensor may be damaged, worn out, or improperly calibrated, leading to low voltage readings.
  • Wiring Problems: Damaged, frayed, or corroded wiring between the TRS and PCM can cause an intermittent or low voltage signal.
  • Poor Electrical Connections: Loose or corroded electrical connectors can disrupt the flow of the sensor's signal.
  • Water or Dirt Contamination: The TRS or its wiring may be exposed to water, dirt, or debris, affecting the electrical components.
  • PCM Malfunction: In rare cases, the PCM itself could be malfunctioning, misinterpreting the signals from the TRS.

Diagnostic Steps

To properly diagnose a P0707 error, a combination of visual inspection and advanced diagnostics is required.

  • Check for Other DTCs: Use an OBD-II scanner to see if any other Diagnostic Trouble Codes (DTCs) are present. Transmission-related codes may indicate multiple issues that need addressing.
  • Inspect the Transmission Range Sensor: Visually inspect the TRS for damage, such as cracks, dirt, or water contamination. Ensure the sensor is securely mounted.
  • Test the Wiring and Connectors: Perform a thorough check of the wiring and connectors between the TRS and PCM. Look for signs of corrosion, broken wires, or loose connections.
  • Check TRS Output Voltage: Use a multimeter to test the voltage output from the TRS and verify if it’s within the acceptable range as per the vehicle’s specifications. If the voltage is too low, the sensor or wiring may need to be replaced.
  • Inspect PCM: If no problems are found with the sensor or wiring, inspect the PCM for software or hardware issues that may be causing it to misinterpret signals.

Solutions

Once the cause of the P0707 code is identified, you can take the appropriate steps to fix the issue. The solutions depend on what is found during diagnosis:

  • Replace the Transmission Range Sensor: If the TRS is determined to be faulty or damaged, replacing it with a new one should resolve the error. Disconnect the negative battery cable, remove the faulty TRS, install the new sensor, and reconnect the battery. Use an OBD-II scanner to clear the code and test the vehicle.
  • Repair or Replace Wiring: If wiring problems are causing the low input signal, the affected wiring should be repaired or replaced. Fix frayed or broken wires, clean corroded connectors, or replace damaged wiring entirely to restore proper electrical flow.
  • Fix Electrical Connections: In cases where loose or corroded connectors are disrupting the sensor signal, cleaning or tightening these connections can resolve the issue. Inspect all connectors along the TRS circuit, clean any corrosion, and secure any loose connections.
  • PCM Reflash or Replacement: If the PCM is faulty or misinterpreting signals from the TRS, it may need to be reflashed (reprogrammed) or replaced, although this is a rare scenario. A professional mechanic will need to perform a PCM reflash or replacement, ensuring proper calibration for your vehicle.

Preventive Measures

To reduce the chances of the P0707 code reappearing in the future, it’s essential to follow these preventive maintenance practices:

  • Regular Inspection: Periodically check the transmission range sensor and wiring for signs of wear, especially in older Ford vehicles.
  • Avoid Water and Dirt Contamination: Keep the sensor and its components free of water and dirt exposure, which can lead to corrosion and signal issues.
  • Routine Servicing: Follow the manufacturer’s recommended service intervals for transmission maintenance to avoid premature wear and electrical failures.

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