P0868 Code: Transmission Fluid Pressure Sensor Low

Finding out what a trouble code means is the very first step in getting it resolved. One of those codes you may encounter is P0868. This article can help you learn more about the definition, causes, and symptoms of the P0868 code.

What Does the P0868 Code Mean?

Diagnostic trouble code (DTC) P0868 code stands for “transmission fluid pressure sensor low.” This trouble code is typically triggered when the powertrain control module (PCM) detects that transmission fluid pressure is low.

The code points to a pressure sensor on some platforms and actual low pressure on others. Ford defines it as a low pressure concern related to the transmission fluid pump, fluid contamination and/or a clogged fluid filter.

Fluid pressures vary from platform to platform. For example, this table provides the proper fluid pressures (measured at the external test port) on a 2017 Ford F150.

The transmission has a fluid pump that provides hydraulic pressure, which is necessary for gear shifts. It’s also responsible for lubrication and cooling. Fluid pressure needs to always be maintained at a certain threshold for the transmission to work properly. If there isn’t enough transmission fluid pressure, then the transmission might not maintain the selected gear.

The PCM can change gears by directing fluid into various hydraulic passages using electronically-controlled solenoids and valves. Transmission fluid pressure is typically provided by an internal pressure pump, which is driven by the engine. When there isn’t enough pressure, then the PCM will no longer be able to change gears because there is a minimum amount of pressure required to initiate a gearshift. At the same time, pressure is also needed to keep the gear engaged.

You can find more technical information that can help you better understand P0868 in our in-depth discussion about fluid pressure.

P0868 on Some Dodge Vehicles

The code appears in a 2013 Dodge Grand Caravan SXT 3.6L because of the following conditions:

• Check for related DTCs
• Low fluid level
• 5-volt supply circuit open
• 5-volt supply circuit shorted to ground
• 5-volt supply circuit shorted to voltage
• LP VFS control circuit shorted to another circuit
• Internal transmission issues
• Line pressure sensor issues
• Cracked, plugged, or mis-installed primary oil filter
• Stuck or sticking main regulator valve
• Powertrain control module (PCM) issues

Note: The definition of P0868 code may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Possible Causes of the P0868 Code?

As previously mentioned, the P0868 code is triggered by low transmission fluid pressure. However, it can also be caused by issues such as:

• Defective transmission fluid pressure sensor
• Damaged wiring or connectors
• Low fluid levels caused by fluid leaks
• Dirty or contaminated transmission fluid
• Defective transmission fluid temperature sensor
• Pressure pump failure
• Faulty PCM

What are the Possible Symptoms of the P0868 Code?

When the P0868 code is triggered, you’ll likely experience symptoms such as:

• Illuminated check engine light
• Gears slipping
• Transmission might not be able to switch into gear
• Transmission overheating
• Vehicle turning on limp mode
• Transmission damage

How to Diagnose the P0868 Code

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: For code P0868, you most likely need to let a transmission shop do the heavy lifting. Exceptions would be an electrical concern related to the solenoid due to a broken wire, but even that type of repair requires a professional.

Keep in mind that identifying the faulty part when you get a P0868 code can be a difficult process because the transmission of most vehicles requires expertise to access. You might need a lot of time and labor to be able to disassemble it for inspection. To get a proper diagnosis, you might want to consult a professional.

If you want to get a better idea of the diagnostic process, you can watch the videos below:

How to Fix the P0868 Code

When you have a P0868 code on your hands that immediately returns after resetting the trouble codes and restarting your car, it’s time to track down the problem’s source.

Transmission Fluid

Always start by inspecting the transmission fluid for issues. Check the lubricant’s color and clarity. If the transmission fluid looks old or dirty, replace it with fresh lubricant.

Next, pull out the dipstick to see how much transmission fluid remains in the reservoir. An abnormally low fluid level indicates a leak somewhere in the system.

Go over the transmission to locate the leak. You can usually find it by looking for dripping transmission fluid. Follow the trail of leaked fluid to the affected part.

Take the appropriate steps to patch the leak. If you can’t repair the damage, replace the leaking part.

Transmission Fluid Sensor and Transmission Fluid Temperature Sensor

If there’s nothing wrong with the transmission fluid’s condition or level, move on to the sensors associated with the system. A faulty transmission fluid sensor can send inaccurate readings that supposedly show the lubricant level has reached dangerously low levels.

Likewise, a bad transmission fluid temperature sensor can mislead you with incorrect data. It might claim the transmission runs hot, an issue often caused by low lubricant levels.

Run tests on both the transmission fluid sensor and transmission fluid temperature sensor. The scan tool will bring up any trouble codes triggered by either sensor. If one of the sensors proves faulty, replace it.

Transmission Wiring

Many wires run through the automatic transmission. They carry current that powers various parts and electrical signals to and from the transmission. These wires are vulnerable to corrosion and physical damage from debris kicked up by the tires.

Check the transmission wiring for any corroded or damaged parts. If you don’t find any issues, move on to the other wires and their connectors.

It’s sometimes possible to remove corrosion, although you must exert care to avoid damaging the affected parts. In most cases, you’ll usually need to replace corroded or damaged wiring.

Internal Transmission Components

One of the transmission’s internal components might have failed at some point. For example, the transmission pump might have stopped working. Diagnose these parts and see if you need to replace one of them.

Powertrain Control Module

The issue might lie with the PCM that controls the automatic transmission. Usually, the computer self-diagnoses and logs the appropriate trouble code if it finds anything wrong with itself. However, there’s always a chance that the PCM failed to set a code. In most cases, you must replace the entire control module.

Transmission Replacement

In some cases, transmission fluid leaks from many parts of the transmission. Multiple leaks suggest that the transmission has sustained severe damage. If you come across many leaks, you must replace the entire transmission.

After identifying, resolving, and repairing the issue that triggered the P0868 code, run a test on the transmission again. If the trouble code doesn’t return, consider the diagnosis complete.

An In-Depth Look at Fluid Pressure

Older automatic transmissions depend on fluid pressure just as much as newer platforms, but on those, the pressure is regulated mechanically. There is line pressure and governor pressure on an older automatic transmission. Governor pressure is tied to vehicle speed, and as the output spins faster, centrifugal force in the governor moves spool valves, channeling fluid so that it moves other spool valves against springs in the valve body to direct fluid through channels and passages to feed the clutches, servos, bands, etc. so as to provide the various gear ranges by way of the planetary gearset.

Line pressure works against governor pressure on those older units and line pressure is controlled by a modulator valve (a vacuum diaphragm connected by a hose to engine vacuum working with a spool valve) or a throttle valve that raises pressure with throttle angle.

As line pressure increases, it opposes governor pressure, which continues to increase with vehicle speed until the transmission is forced to shift to the next gear. Thus shifts are delayed, because when the engine is loaded (pulling a trailer or on hard acceleration or going up a hill or all of the above), the transmission needs to delay its shifts to keep the engine in its power band.

On newer automatic transmissions, fluid pressure is totally controlled by an electrically driven variable force solenoid (or equivalent) that operates on a duty cycle from the PCM or TCM. Throttle angle and vehicle speed are electrical signals, as is fluid temperature and other factors providing the PCM or TCM the input it needs to properly control transmission fluid pressure. In addition to the pressure control solenoid, there are shift solenoids and usually a solenoid to modulate the torque converter lockup by percentage.

If the pressure control solenoid loses power, the fluid pressure defaults to maximum pressure to protect the clutches. Of course, if the pump has failed or isn’t working right or if it’s starving for fluid, this kind of issue will typically set a P0868 code.