A P0705 code is a generic powertrain code that can be triggered in select vehicles built from 1996 onward. This OBD-II code may present common symptoms in different types of vehicles, but diagnosis and repair may vary for each specific make and model.
What Does the P0705 Code Mean?
Diagnostic trouble code (DTC) P0705 code stands for “Transmission Range Sensor Circuit Malfunction (PRNDL Input).” It is triggered when the transmission range sensor cannot send data or provides erroneous input to the transmission control (TCM) or powertrain control (PCM) modules.
The transmission range sensor may also be called the neutral safety switch or PRNDL input. Located outside the transmission box or on the valve body, its job is to communicate the current gear selection or shift lever position with the TCM or PCM.
To learn more about how transmission range sensors work, you can read our in-depth explanation here.
What are the Possible Causes of the P0705 Code?
There are two scenarios that could cause a vehicle’s OBD-II system to log a P0705 code. The first is when the TCM and PCM do not receive any information from the transmission sensor at all.
The second is when these modules receive an irrational input from the sensor.
An example could be if the vehicle is running at 70 mph, but the sensor signals the TCM that the car is in park. Likewise, this diagnostic trouble code will trigger if the sensor sends signals that indicate that the vehicle is in multiple gears at the same time.
Here are the common problems that can cause missing/faulty readings from the transmission range sensor:
- Malfunctioning transmission range sensor (PRNDL input)
- Issues with the transmission range sensor circuit, such as damaged wires or poor connections
- Defective valve body
- Defective shift linkage
- Faulty TCM or PCM
What are the Common Symptoms of the P0705 Code?
A P0705 trouble code may cause performance problems that would be noticed by the driver. Below are some signs that you should look out for:
- Check Engine Light is on or blinking
- Rough or delayed shifting
- Failure to put the vehicle into gear
- Erratic dash indicators (PRNDL)
- Reverse lights don’t switch on
- Vehicle starts with the gear selector in a position other than park or neutral
Occasionally, a malfunction in the transmission range sensor circuit may occur without any adverse effects that affect the drivability of your vehicle.
How to Diagnose the P0705 Code
There are a lot of possible causes that could trigger the P0705 code, so diagnosis can get a little tricky especially if you’re not very car-savvy. This is why most people just leave the job to their mechanic.
However, you can still do the job yourself with the help of a detailed guide. Below is a helpful video with more information to help you diagnose the P0705 code:
How to Fix the P0705 Code
There’s no one-size-fits-all solution for the P0705 code—just like with most OBD-II codes. Most people simply take their cars to their mechanics and leave the job to them. However, if you feel confident in your DIY skills or are looking to learn more about auto repair, then you can try taking the task on yourself.
To figure out the appropriate fix for the P0705 code, do some research on forums and other similar platforms to see what other car owners (who own the same vehicle, of course) have done to successfully clear the code.
It’s important to note that different vehicles may involve different fixes. For example, replacing the transmission range sensor has been confirmed to work in fixing a P0705 code on a 2011 Ford F-150, XL 5.0L, V8, but doing the same thing may not work for your vehicle.
Other Tips to Help You Fix P0705
On vehicles where the Transmission Range sensor is integrated with the Transmission Control Module, some programming may be required, so don’t try that on your own. One way or another, you need to find out everything you can about how your particular TR sensor works and how it is wired. And if that isn’t enough, sometimes the TR sensor is very difficult to access, particularly on front wheel drive vehicles.
Thus, when doing any DIY work on your vehicle, always make sure to consult repair manuals and credible online guides. When you try to “wing it,” you can make a lot of problems for yourself that you didn’t have before.
You can get an ALLDATA single-vehicle subscription, which should give you the information you need for this and any other future repairs your car may need.
An In-Depth Look at How Transmission Range Sensors Work
To begin with, it bears mention that the automatic transmissions and transaxles in new vehicles, while still mostly hydraulic, have solenoids that facilitate transmission shift functions, and those solenoids are controlled by the vehicle’s Powertrain Control Module (PCM) or by a Transmission Control Module (TCM). The Engine Control Module (ECM) only controls the engine; a vehicle with an ECM and an automatic transmission will have a stand alone TCM. Jeep Cherokees used this setup beginning in the 80s.
On newer vehicles, the ECM and TCM will share pertinent information on the network bus. A PCM controls both the engine and the transmission, but as the demands on the PCM increased with each new model year, manufacturers separated engine and transmission controls into separate modules, thus the TCM.
How Transmission Range Sensors Developed
Okay, whenever there’s a computer controlling the transmission shift points and line pressure, that computer needs to know where the gear selector is at all times. So how does it do that?
Very early model Fords without electronic transmissions only need to know when the selector is in Park or Neutral, so the ECM (Ford referred to it then as a “Processor”), is watching the starter solenoid wire between the ignition switch and the neutral safety switch, which is where the Transmission Range Sensor is on newer vehicles.
When the transmission is in Park or Neutral, the ECM will detect a ground path through the starter solenoid – in any other gear it won’t. That information is used for idle speed control and other load-related functions on those vehicles.
But as solenoids and speed sensors took root in transmissions and transaxles in the 1980s, it became clear that the PCM needs to know exactly where the gear selector is at all times. And the engineers decided how best to do it on their various platforms; it is handled several different ways. We don’t have time to discuss them all, but here are a few.
How Transmission Range Sensors Operate on Different Platforms
The Transmission Range Sensor is usually mounted on and keyed to the shift rail, which rotates through shifter detents when you make your gear selection – detents being those places where you can feel the shifter “click” through the gears on the way to the position you want and finally into the one you have selected.
- Mid-80s Ford Tauruses used a transmission range sensor that operates similar to a throttle position sensor – it receives reference voltage and ground from the PCM and has a signal wire returning shift rail position to the PCM. A graph of this voltage signal looks like stair steps; the PCM knows the gear selector position by the voltage level on the signal wire. That signal could get “scratchy” and give the PCM bad information, but on that system, it would take a near total failure of the sensor before the PCM could detect it.
- Later model Fords used a digital transmission range sensor with four on-off switches. This kind of signal is much easier for a computer to process, because computers are basically binary code readers, and the on-off switches provide a four digit binary code. This arrangement is very reliable and gives almost no trouble; you can recognize this kind of Range Sensor due to the large number of wires in the connector (usually 12).
- The 2012 Camry has a very simple arrangement whereby the transmission range Sensor has a single system voltage feed to the sensor, and in each selected gear feeds that voltage out to the PCM on a different wire. It’s fairly easy to understand how the PCM can determine when the Range Sensor or its circuits have malfunctioned on a setup like this. The computer expects to see a brief voltage flash at each position followed by a steady voltage feed from the gear selected. This Transmission Range Sensor uses 8 wires, one voltage feed in and 7 discrete feeds out to the PCM.
- The newest vehicles will have the transmission control module mounted in or on the transmission or transaxle and the transmission range sensor will be integrated into the computer itself.
This could go on for pages, but you get the point. Not all transmission range sensors work the same way, even though they do the same job. Neutral safety and backup light functions are obviously tied to switch position as well.
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