The OBD-II trouble code P0705 indicates a “Transmission Range Sensor Circuit Malfunction (PRNDL Input)”. This generic powertrain code applies to all makes and models from 1996 onwards equipped with OBD-II, but specific diagnostic steps can vary depending on the vehicle. As an expert at autelfrance.com, let’s delve into the details of this code, providing you with a comprehensive understanding and troubleshooting guide.
Understanding the Transmission Range Sensor (TRS)
The Transmission Range Sensor (TRS), sometimes referred to as the Neutral Safety Switch or Park/Neutral Position (PNP) switch, is a crucial component in your vehicle’s transmission system. Its primary function is to inform the Powertrain Control Module (PCM) or Transmission Control Module (TCM) about the gear shift lever position. This includes positions like Park (P), Reverse (R), Neutral (N), and Drive (D), often represented as PRNDL. In some vehicles, the TRS also activates the backup lights when the vehicle is in reverse.
The P0705 code is triggered when the vehicle’s computer detects a discrepancy or failure in the signal from the TRS. This means the sensor is either sending an incorrect signal or no signal at all regarding the gear position. The computer relies on input from both the TRS and the vehicle speed sensor to accurately determine the vehicle’s operating state.
For example, if the TRS signal indicates the vehicle is in “Park,” but the speed sensor shows the vehicle is moving, the PCM will recognize this contradiction and set the P0705 code. This code signals a potential issue within the TRS circuit that needs attention.
Symptoms of a P0705 DTC
When the P0705 code is set, you may experience a range of symptoms affecting your vehicle’s performance and functionality. These can include:
- Malfunction Indicator Lamp (MIL) Illumination: The check engine light on your dashboard will illuminate, indicating a problem.
- Backup Lights Malfunction: Your reverse lights may fail to turn on when you shift into reverse.
- Starting Issues: You might need to wiggle the gear shift lever to find the “sweet spot” for the starter to engage, allowing the engine to start.
- No Start Condition: In some cases, the vehicle may not start at all.
- Starting in Neutral Only: The engine might only start when the gear shift is in the Neutral position.
- Starting in Any Gear: Conversely, the vehicle might start regardless of the gear selector position, which is a significant safety concern.
- Erratic Shift RPMs: The transmission may shift gears at irregular RPMs, leading to jerky or unexpected gear changes.
- Reduced Fuel Economy: Inefficient gear shifting can negatively impact fuel consumption.
- Delayed Transmission Engagement: You may notice a delay between shifting into drive or reverse and the transmission engaging.
- Erratic Instrument Readings (Toyota Vehicles): Toyota vehicles, including trucks, may exhibit unusual readings on the instrument cluster.
Potential Causes of the P0705 Code
Several factors can lead to a P0705 trouble code. Identifying the root cause is crucial for effective repair. Common causes include:
- Misadjusted TRS: The Transmission Range Sensor may be loose or improperly adjusted, leading to incorrect signals.
- Defective TRS: The sensor itself might be faulty and failing to send accurate data.
- Connector Issues: A bad connector at the external TRS, including loose, corroded, or bent pins, can disrupt the electrical signal.
- Wiring Harness Damage: A shorted wiring harness on an external sensor, often caused by rubbing against the transmission linkage, can cause circuit malfunctions.
- Internal Valve Body Issues: For vehicles with internal TRS, a blockage in the valve body port or a defective internal sensor can trigger the P0705 code.
Diagnosing and Repairing the P0705 Code
Diagnosing and repairing a P0705 code requires a systematic approach. The repair process largely depends on whether your vehicle has an external or internal Transmission Range Sensor.
External Transmission Range Sensor: Diagnosis and Replacement
External TRS units are typically mounted on the outside of the transmission and are more accessible. Here’s a step-by-step guide for diagnosis and potential replacement:
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Safety First: Block the wheels and engage the parking brake to prevent vehicle movement.
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Shift to Neutral: Place the transmission gear selector in the Neutral position.
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Locate the TRS: Identify the transmission shift linkage. On front-wheel-drive vehicles, it’s usually on top of the transaxle. Rear-wheel-drive vehicles typically have it on the driver’s side of the transmission.
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Inspect the Electrical Connector: Carefully disconnect the electrical connector from the TRS sensor. Thoroughly inspect both the sensor and harness connectors for corrosion, bent pins, or pushed-out terminals. If the harness connector is damaged but the wiring is intact, it can often be replaced separately. Apply a small amount of dielectric grease to the connector before reconnecting to prevent future corrosion.
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Check Wiring Harness: Examine the wiring harness for any signs of damage, such as rubbing against the shift linkage, broken wires, or worn insulation that could cause a short circuit.
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Check for Loose Sensor: See if the TRS sensor is loose. If it is, with the parking brake still engaged and the transmission in neutral, turn the ignition key to the “ON” position. Gently rotate the TRS until the backup lights illuminate. Once the backup lights are on, tighten the sensor’s mounting bolts. For Toyota vehicles, the adjustment procedure might involve inserting a 5mm drill bit into a specific hole on the sensor housing before tightening. Refer to your vehicle’s service manual for precise instructions.
Image of an External Transmission Range Sensor. Alt text: External Transmission Range Sensor (TRS) commonly found on older vehicles, highlighting the electrical connector and mounting points.
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Remove Shift Lever (If Necessary): If replacement is needed, remove the nut securing the gear shift lever to the TRS and detach the lever.
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Disconnect Electrical Connector (Again): If not already done, disconnect the electrical connector from the sensor.
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Remove the Old Sensor: Unscrew and remove the bolts holding the TRS to the transmission. Be extremely careful not to drop these bolts, as retrieving them from the transmission area can be time-consuming and frustrating.
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Install the New Sensor: Compare the new sensor to the old one. Ensure that the alignment marks on the sensor shaft and housing (often marked “Neutral”) are correctly aligned. Mount the new sensor onto the shift lever shaft and tighten the mounting bolts to the specified torque.
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Reconnect Electrical Connector: Plug the electrical connector back into the new sensor.
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Reinstall Shift Lever: If removed, reattach the shift lever and tighten the retaining nut.
Internal Transmission Range Sensor: Diagnosis and Repair
Internal TRS units are located inside the transmission valve body, making them less accessible and more complex to service. Diagnosing an internal TRS often requires specialized tools like a Tech II scan tool for accurate readings. Repair typically involves draining the transmission fluid, removing the transmission pan, and accessing the valve body.
Internal TRS sensors are continuously immersed in transmission fluid, which can lead to issues over time. Problems can arise from restricted hydraulic fluid flow or failing O-ring seals. Due to the complexity and potential for transmission damage, repairing or replacing an internal TRS is best left to a qualified transmission specialist.
Important Note: Some Ford vehicles may refer to the external TRS as a Manual Lever Position Sensor (MLPS).
Related OBD-II Trouble Codes: P0706, P0707, P0708, and P0709 are related codes that indicate other issues within the Transmission Range Sensor circuit.
Need Further Assistance with P0705?
If you require more in-depth help with diagnosing and resolving the P0705 trouble code, we encourage you to visit our FREE car repair forums and post your question. Our community of experienced technicians and DIY enthusiasts is ready to assist you.
Disclaimer: This information is intended for informational purposes only and should not be considered professional repair advice. We are not liable for any actions taken based on this information. Always consult a qualified technician for vehicle repairs. All content is copyright protected.
