Looking for the meaning of P0705 code? You’re in the right place. In this article, we talk about the meaning, cause and possible solutions to the “Transmission Range Sensor Circuit Malfunction”, or P0705 Code.
Meaning and Cause of P0705 Code
First things first – is this a generic or a manufacturer-specific Diagnostic Trouble Code (DTC)? Because it starts with P0xxx, the P0705 is a generic powertrain code, meaning it covers all vehicles with OBD-II systems, or all newer makes and models (1996 and newer). Normally, generic DTCs will exhibit similar symptoms across all newer vehicles, however, the specific diagnostic and repair steps will vary from model to model.
What Does the P0705 Code Mean?
This DTC indicates a problem with a part of your vehicle known as Transmission Range Sensor or Transmission Gear Position switch. Another common name for this part is Park Neutral Position switch, or PNP switch. When the Transmission Control Module (TCM) receives an erroneous input from this particular sensor, your Engine Control Module (ECM) will light up your Check Engine Light.
To explain in more detail, we need to address the location and function of the Transmission Range Sensor (TRS). Usually, it’s found on the outside of the transmission box, but sometimes, it can be located inside the transmission on the valve body. Its function is to inform the TCM, and by extension the ECM, of gear selection or the position of the shift lever. If the ECM doesn’t receive an input, P0705 occurs. There is another way this DTC may set – if the ECM receives an illogical input. For instance, if you’re driving 60 mph but the TRS informs the ECM that the vehicle is in reverse, the code P0705 will occur. Likewise, if the TRS becomes so faulty that it tells the ECM that it’s in more than one gear at the same time, the code P0705 will set.
Finally, there are different types of TRS and it’s important to differentiate between each as diagnostic and repair steps will vary from type to type:
- The Contact TRS
This type consists of a set of wires that communicate with the ECM, letting it know the exact shift lever position. This is possible because each position of the shifter has its own wire.
- The Pressure Range Switch
This type is mounted on the valve body of the transmission. There are various passages for the transmission fluid which get open and closed as the shifter is moved, which is how this type of the sensor knows when the position moves.
- The Variable Resistor
Containing a series of resistors tied to one voltage output, this type is designed to absorb a certain amount of voltage. Because each gear has its own resistor that will be used depending on the shifter positioning (park, reverse, neutral, drive, low, or PRNDL), the sensor knows when and which position moves.
But What Causes the Code P0705?
Sine there are several types of the TRS, there can be various causes for the occurrence of this DTC. The most common ones include:
- Short or open in the TRS circuit
- Loose or damaged TRS
- Defective transmission range sensor
- Loose or damaged connector at the external TRS
- Misadjusted shift linkage
- Contaminated/bad transmission fluid
- Blockage in the internal valve body TRS port
- Faulty transmission valve body
- Low voltage
- Damaged TCM or ECM (rare)
Symptoms of the P0705 Code
The P0705 code can have a variety of symptoms, including the following:
- Check Engine Light is on
- The vehicle may experience a no start condition
- Harsh/erratic shifting
- The vehicle may start in any gear
- Poor fuel economy
- The car may only start in neutral
- No reverse lights
- The vehicle may not go in or out of gear
Diagnosing and Repairing the P0705 Code
Although a very common cause for this DTC is a defective TRS, this is not always the case. Often, the problem will lie in a misadjusted TRS, where the solution is to simply adjust it. However, mechanics will sometimes replace the sensor in error. This is a costly mistake. Another common mistake when diagnosing the P0705 code is not checking the fluid level and condition. If the fluid is low, contaminated or both, the code P0705 code can occur, plus several other problems. To avoid these common but easily solvable issues, it’s crucial to start and perform the diagnostic and repair process following the right steps.
Note: If you have an extensive auto knowledge, you may be able to do this with the help of a friend. Otherwise, it’s highly advisable you hire a professional as diagnosing and repairing P0705 code can be tricky.
- Plug the OBD-II scanner into the DLC port. Record all stored codes and freeze frame data.
- Start the inspection by checking the fluid level and condition, as well as the condition of the transmission. If all is well there, inspect the electrical connection on the TRS. This is especially important if the switch is mounted externally because it’s susceptible to road dirt, grime and moisture which can damage the connection. Also, verify that the TRS has a proper voltage.
- For the Contact type TRS
Probe each wire, and at the same time, change the gears to verify there is correct output (this is why at least two people, preferably mechanics should do the inspection, diagnosis and repair of this DTC). If all works well, there will be a change in the voltage every time the gear position is changed.
- For the Variable Resistor Type
Using a multimeter, measure the amount of voltage that the reference wire outputs. This needs to be done because the reference wire sends a different voltage to the ECM every time the gear is changed. So, if the voltage doesn’t change or appears to be nonexistent, the problem is either in the sensor itself or reference wire.
- For the Pressure Range Switch Type
Because most of these types of sensors use a ground connection as their form of output, a mechanic needs to verify which wires are actually output to ground. To do this, gear position needs to be changed so that the valve body lets the transmission fluid go through different passages. As it travels through one of the passages, the TRS will output that ground. Of course, to find out which wire corresponds to which gear, you’ll need a wiring diagram of the sensor.
So, the following fixes can help resolve the P0705 code:
- Repairing a short or open in the TRS circuit
- Adjusting a misadjusted TRS
- Replacing a damaged TRS
- Changing the transmission fluid and/or filter
- Rarely, replacing the (faulty) ECM.
Additional Information about the P0705 Code
Because there are different types of TRS, inspecting, diagnosing and repairing P0705 may require a lot of work. For this reason, and also because two people are usually necessary to inspect the vehicle, it’s recommended you hire a professional to deal with this DTC.
These links will provide more detailed insights into what code means in your vehicle:
Be sure to also read our essential guide to the best OBD2 Scanner.