The P0705 code indicates an issue with your transmission range sensor circuit. This is the part of your car that tells the ECM what gear your transmission is in. When something goes wrong, your car may refuse to change gears or even start. That makes fixing this code a high priority.
There are a variety of repairs that could clear the P0705 trouble code. Read on below to learn more about the transmission range sensor and how to diagnose and repair it.
P0705 Code Definition
P0705 Code Definition (Generic): Transmission Range Sensor Circuit Malfunction
P0705 Ford Code Definition: Evaporative Emission (EVAP) control system malfunction (small leak, neg pressure test)
P0705 Honda Code Definition: A/T Range Switch Short
What Does P0705 Mean?
The P0705 OBD2 code is a generic powertrain code. This means it applies to all vehicles. Having said that, it often has different fixes depending on your make and model. You should check your vehicle manual for specific repair suggestions before starting the generic diagnosis below.
The transmission range sensor (TRS) is usually located on the outside of the transmission box. In some vehicles, it’s instead inside the transmission, often on the valve body. It exists to tell the transmission control center (TCM) the position of the shift lever and gears. This information is then sent on to the engine control module (ECM).
When the ECM gets an erroneous input from the transmission range sensor, the P0705 OBD2 code is triggered. In some cases, when the TRS is faulty, it may report that the engine is in multiple gears at once.
You may also hear the TRS called the Park Neutral Position (PNP) switch. There are also different kinds of TRS:
- Contact TRS. These consist of a set of wires, with one for each position of the shifter. These wires are responsible for telling the ECM where the shift lever is.
- Pressure Range Switch. These are normally mounted inside the transmission rather than on the box. They use passages filled with transmission fluid, which are opened or closed when the shifter moves.
- Variable Resistor. These TRS types use a series of resistors connected to a single voltage output. There is a resistor for each gear. How much voltage each resistor absorbs tells the ECM which position the switch is in.
What kind of TRS you have will affect how you conduct your diagnosis and repair. If you’re not sure which one your car has, you can check your manual.
What Are The Symptoms of The P0705 Code?
In some cases, you may not be able to start your vehicle. This happens when the TRS erroneous reports the car is in gear. Most vehicles won’t start unless they’re in park or neutral. Other symptoms of P0705 include:
- Activation of the check engine light
- Difficulty changing gears
- Inability to change gears
- Irregular changes in the RPM
- Reduced fuel economy
- Erratic instrument readings (especially Toyota trucks)
What Are The Causes Of P0705?
- Loose or poorly adjusted TRS
- Defective TRS
- Loose or damaged wires around the TRS
- Corroded or bent connector pins
- Shorts in wiring harness
- Blockage in internal TRS valve body
How Serious is the P0705 Code?
The P0705 code is moderately serious. Because erratic shifting may occur, you should not drive your vehicle until you’ve repaired the problem. Your vehicle may also go into “limp mode,” which prevents you from going above 40mph. While long-term damage to your engine is unlikely, you should repair the problem as soon as possible.
How To Diagnose And Fix The P0705 Code
Tools you’ll need:
- Check the freeze frame data using the OBD2 scan tool. This should help you identify the conditions under which the code is occurring.
- Check the level and condition of your transmission fluid. Good transmission fluid is clear and bright. If it’s brown, cloudy, or has visible debris floating in it, replace the filter, flush your system, and replace it with new fluid.
- Inspect the electrical connections and wires around the TRS. Sensors mounted to the outside of the transmission box are especially susceptible to damage from dirt and moisture.
- Check the alignment of the TRS, and adjust as necessary.
- Use the digital multimeter to test the TRS. You can find the correct voltage in your vehicle manual.
- The next step varies depending on what kind of TRS you have:
- Contact-type TRS: Probe each wire of the TRS while changing gears. The voltage should change each time you change gears. If it doesn’t, the TRS is defective.
- Variable Resistor TRS: Measure the voltage of the reference wire outputs with a digital multimeter. If it doesn’t change when you change gears, the problem may be with the reference wires or the TRS. Replace the wires first, as these are the easier and more affordable repair. If that doesn’t fix the problem, replace the TRS.
- Pressure Range TRS: These wires use a ground connection for output, so the first step is to verify which wires are the output. Change gears to allow the transmission fluid through the passages. The TRS will output a ground as the fluid passes through. If it doesn’t, the sensor is defective.
- If the code still won’t clear, you may have a more serious electrical issue. Take your vehicle to a mechanic for further diagnosis.
Common Mistakes To Avoid While Diagnosing The P0705 Code
Be sure to check the wires around the TRS and harness before you replace the sensor itself. Shorts and corrosion in the wiring are just as likely to be the cause as the sensor. Also make sure you check the adjustment of the shift linkage and the condition of your transmission fluid.
Tips To Avoid P0705 in The Future
Make sure to check your transmission fluid when you change your oil, refilling if the level is low and replacing if the fluid is dirty or corrupted. Bad transmission fluid can cause problems with the TRS, and other systems as well.