P0705: Transmission Range Sensor Circuit Malfunction

What is P0705?

Diagnostic Trouble Code (DTC) P0705 is defined as “Transmission Range Sensor Circuit Malfunction (PRNDL Input).” It’s a generic OBD-II code applicable to vehicles with automatic transmission.

The transmission range sensor (TRS) is responsible for telling the transmission control module (TCM) or engine control module/powertrain control module (ECM/PCM) the position of the gear shift lever. The TRS has many names, like: 

• Transmission range selector sensor
• Neutral safety switch 
• Park/Neutral safety switch
• Park/Neutral position sensor
• Gear selection switch
• PRNDL input switch

The TCM or ECM uses data from several sensors (like the TRS, speed sensor, and throttle position sensor) to control which transmission gears to enable seamlessly. 

Fault code P0705 occurs when the TCM or ECM receives an input error from the TRS sensor. This happens when a faulty transmission range switch fails to send an input to the ECM. Alternatively, it could send an illogical input, such as reporting that the vehicle is in Reverse when the selector lever is in Drive.

The engine control module will trigger code P0705 and turn on the check engine light for either condition. It’s also relatively common for the traction control light to turn on along with the engine light when this happens, especially in Toyota Motor Corporation vehicles.

P0705 Causes

Many factors could cause DTC P0705, not just a faulty sensor.
Some potential faults include:

• A short, torn harness or frayed wire in the transmission range sensor circuit
• A misadjusted transmission range sensor
• A misaligned wire harness connector at the shift linkage cables
• A fault in the transmission valve body
• Old or dirty transmission fluid

P0705 Symptoms

DTC P0705 can cause some noticeable problems in your automatic transmission vehicle. Here are the more common ones:

• Vehicle may not start: The TRS acts as a neutral safety switch, only allowing the car to start in the Park or Neutral position for safety reasons (which is why it’s also called an inhibitor switch). If the TRS can’t accurately report the gear position, the vehicle may not start when you fire the ignition.

• Difficulty shifting gears: You may struggle to get your car in or out of gear. Gear changes may be rough or delayed.

• Reverse light doesn’t illuminate: The reverse light (backup light) may not activate if the ECM doesn’t receive input that the car is in Reverse gear.

• Gear position displays incorrectly: If your car has a gear indicator, it may not show the correct gear shifter position.

• Check engine light (CEL) or transmission light is on: A lit engine warning light indicates an engine problem. A mechanic can tell you if the trouble code is P0705.

Can I Still Drive?

It’s often not possible to drive with a P0705 code, though this may not always be the case. 

A faulty transmission range sensor will likely affect the vehicle’s ride quality.
For example:

• The engine might not crank when you turn on the ignition (because the TRS or inhibitor switch isn’t sending the correct signals.)
• You may experience erratic transmission shifts, which could be dangerous.
• The engine may stall more frequently.
• The car may enter “limp mode” (or failsafe mode), limiting your speed to 40mph.

Driving your car in this condition can cause serious damage to other engine parts. It’s recommended to take your vehicle to a mechanic ASAP.

Diagnosing Code P0705

To identify what code is causing the check engine warning light, you can use an OBD II scanner. This will tell you if the problem is a P0705 Transmission Range Sensor Circuit malfunction.

However, troubleshooting the root cause of the error may require specialized knowledge and tools, so it’s best to get a mechanic’s expert help rather than DIY.

Here’s how a mechanic would diagnose error code P0705:

1. Identify the transmission range sensor type: There are three types, each requiring a slightly different approach to repairs. The types are:

• Contact TRS: Each gear position has a separate wire to specify the position on the gear indicator.
• Pressure Range Sensor / Pressure Range Switch: The sensor is positioned on the transmission valve body, opening and closing a different passage for each gear position. Transmission fluid flows through an open passage to indicate the gear shifter position.
• Variable Resistor TRS: Each gear shift lever position has a different standard resistance. The effect on the current flowing through the system indicates the shift lever position.

2. Inspect the tail light: Sometimes, humidity in the tail light can create shorts that cause the P0705 code. Check for cracks or signs of moisture.

3. Check the transmission fluid: Ensure that the level and condition of the transmission fluid are as required.

4. Ensure that the transmission range sensor is properly connected: The problem may be caused by a misaligned connector.

5. Test the voltage and ground at the TRS sensor: The mechanic can use a multimeter to test the voltage output for each gear. The process is different for each of the three TRS types:

• Contact TRS: Measure the voltage on each wire while someone changes gears.
• Pressure Range Sensor: Measure the voltage on the reference wire. The voltage should be different for each gear selector lever position.
• Variable Resistor TRS: Measure the change in voltage on the ground wire corresponding to each gear selector lever position. Use a wiring diagram to see which wire is which.

6. Check for standard resistance if the voltage is low (but not zero).

7. Inspect the transmission range sensor circuit: If the voltage and ground seem sound, the mechanic will need to inspect the entire TRS circuit. 

Check the harness for frayed wires and look for breakages in the harness. Inspect the TRS circuit for blown fuses, a faulty electrical connector, and anything that could disrupt the continuity in the wiring harness.

Your mechanic should perform each check correctly to avoid unnecessary expensive repairs. For example, they should properly inspect the wiring harness continuity, transmission fluid, and electrical connector alignment before diagnosing a faulty transmission range sensor or replacing any parts.

Possible Repairs for P0705 & Costs

Fixing error code P0705 may require repairing or replacing one or more of the following:

• Dirty transmission fluid (inexpensive but should be done regularly)
• Faulty TRS circuit wiring (inexpensive but labor-intensive)
• Linkage between the selection lever inside the car and the shift lever on the transmission (inexpensive but labor-intensive)
• Misadjusted TRS (inexpensive but labor-intensive)
• Faulty TRS
• Faulty transmission control module (expensive but uncommon)
• Faulty engine control module (expensive but uncommon)

The auto repair cost will include parts and labor charges and may vary based on the make and model of the vehicle. 

Here are some estimates:

• Replacing the TRS: $200-$500
• Flushing and replacing the transmission fluid: $230-$475
• Replacing the transmission valve body: $300-$1000