Transmission fluid pressure sensor

Transmission fluid pressure sensor: In most modern cars, trucks, and SUVs, the transmission and internal components are monitored by a series of sensors and switches that transmit information to the ECM every millisecond. One of these components is the transmission oil pressure switch, which is designed to monitor the amount of pressure built up inside the transmission case as fluid flows through a series of chambers and channels to allow Transmission shifts smoothly. Like any other sensor, it can become damaged or simply wear out.overtime.

What is Transmission Oil Pressure Switch?

The transmission oil pressure switch is connected to the transmission case and is designed to monitor and transmit the oil pressure within the transmission to the on-board computer found in most vehicles. Older vehicles without an ECM also use a transmission oil pressure switch, but instead of sending data to a computer, the information is displayed on a gauge on the dash or sent to a monitoring console that turns on a light on the dash if there is a problem. is detected.

Most of today’s vehicles have multiple sensors that monitor aspects of the transmission, from oil pressure to heat, RPM, and even some that control your vehicle’s cruise control. The transmission oil pressure switch is unique in that its sole purpose is to collect data on the pressure inside the transmission case, which affects timing and the operation of upshifting a vehicle or lower if necessary.

Due to the fact that it is located under the vehicle, the transmission oil pressure switch is subjected to extreme conditions and operates in a harsh environment. It can wear out, break, or fail, causing it to not work at all, or worse, transmitting incorrect data to the vehicle’s ECM, causing the transmission to malfunction and potentially damaging components in the process.

If this component wears out or breaks, it will cause a series of warning signs that can alert the driver that there is a problem with this part and it should be replaced as soon as possible. Mentioned below are some of the indicators that theThe transmission oil pressure switch is damaged and needs to be replaced. by a local ASE certified mechanic.

1. Vehicle enters “limp” mode

The main function of the transmission oil pressure sensor is to transmit information to the ECM which regulates the transmission control. However, if the switch is bad or does not send information correctly to the ECM, the transmission maydefaults to “lazy” mode. In this case, the transmission will lock in the “lazy” gear, such as a higher third or fourth gear ratio, allowing the vehicle to run at a lower RPM while the driver takes the vehicle to a mechanic or back to a mechanic. house. . This will be blocked until a professional mechanic downloads the error codes from the ECM and the issue that triggered the “limp” mode is resolved.

If you’re driving down the highway and your transmission sticks in a higher gear, drive home and contact a professional mechanic to have the problem inspected. The transmission is most likely in this default gear due to a malfunction of some kind that needs to be fixed before driving again.

2. The vehicle has difficulty shifting

One of the most common symptoms of a bad oil pressure switch is a loose wire that is connected to the switch and relays the information to the ECM. When the cable is not secured, it can cause the sensor to register a lower pressure than what is inside the transmission. The computer will notice this faulty information, which may causechanging difficulties (especially downshifting).

3. Engine RPM is higher than it should be

Like the situation above where the transmission has difficulty shifting due to a faulty oil pressure switch, this same issue can cause the transmission to not shift when it should. In this situation, the engine RPM will be much higher than it should be when you engage the transmission to upshift.

The transmission oil pressure switch is vital to the smooth and efficient operation of the vehicle. If you recognize any of the above warning signs or symptoms, contact an ASE Certified Professional Mechanic in your area to have them checked out.replace transmission oil pressure switch as soon as possible if this is really what is causing your problems.


Your vehicle’s transmission allows you to shift gears smoothly. Transmission fluid moves from the master chamber to the slave chamber, building up pressure in the process. The transmission oil pressure switch then measures how much pressure is building up inside the transmission chamber and tells the computer whether or not there is enough pressure to engage the clutch and shift gears.


It is important to note that transmission oil pressure switches are not repairable, but should be replaced when they become faulty. If the damage is severe, the transmission control module may also need to be replaced. These switches are not usually inspected during mechanical services, but regular transmission fluid replacements can prevent damage and failure to your transmission.


According to Your Mechanic, “Most vehicles will never have a transmission pressure switch replaced in their lifetime.” You can preventatively care for your transmission pressure switch with regular transmission fluid changes.

Some signs that it might be time to replace the transmission oil pressure switch are if the “Check Engine” light is on, the transmission shifts hard, won’t upshift, or is in stall mode. emergency.


When you bring your car in for a transmission inspection, the mechanic will first test the transmission oil pressure switch to see if it needs replacement. If it is faulty, the existing switch will be removed and a new one installed. The new oil pressure switch is then tested for proper operation and the transmission itself is tested to ensure proper operation of the oil pressure switch.


Replacing the transmission oil pressure switch can cost between $170 and $300, depending on the make and model of your vehicle, the cost of parts, and the cost of labor. Mechanic labor prices can vary depending on the auto shop you choose, with parts prices going to be higher on newer and luxury vehicles. In general, this service is not extremely expensive, but it is important.


Left unfixed, a faulty transmission oil pressure switch can cause your car to have gearshift problems, damage internal transmission parts, and eventually fail. This service is important in maintaining the health of your transmission and helps ensure that you can shift into higher gears without the “Check Engine” light worrying you.

In short, it is very important to have your transmission serviced when you notice any signs of its degradation. You can schedule a checkup or service at Prieto Automotive through our website, or you can give us a call as the first step in caring for your car!

Cost to Diagnose the P0844 Code

P0844 is a Diagnostic Trouble Code (DTC) for “Transmission Fluid Pressure Sensor/Switch A Circuit Intermittent”. This can happen for multiple reasons and a mechanic must diagnose the specific cause for this code to set in your situation. Our certified mobile mechanics can come to your home or office to perform a Check Engine Light diagnostic for $114.99. Once we are able to diagnose the problem, you will be provided with an advance estimate for the recommended solution and receive a $20.0 discount as credit towards the repair. All of our repairs are backed by our 12-month/12,000-mile warranty.

P0844 Code Definition

Storing a P0844 trouble code means that the Powertrain Control Module (PCM) has detected a deviation in the voltage signal received from the transmission fluid pressure sensor circuit. Some related codes include P0840,P0841, P0842,P0843, P0845,P0846,P0847,P0848, YP0849.

What does the P0844 code mean?

The PCM uses data from the transmission fluid pressure sensor/switch to determine if the correct amount of pressure is present for proper vehicle operation. When the pump pressure varies from what is needed, a P0844 trouble code is stored and the Check Engine light comes on.

What causes the P0844 code?

A faulty electronic pressure control solenoid, a blockage within the transmission fluid passages, a faulty transmission fluid pressure sensor, a low fluid condition, dirty transmission fluid, a mechanical failure of the transmission, or even a faulty PCM or transmission control module (TCM). ) are some common causes for the storage of a P0844 trouble code.

What are the symptoms of the P0844 code?

Symptoms of a P0844 trouble code range from non-obvious signs to theinability to switch correctly, and even a failure of the torque converter to function properly. Some other common symptoms of a P0844 trouble code include difficulty shifting,transmission overheating, and a reduction in vehicle fuel efficiency. Also, when this code is stored, some PCMs can place the vehicle’s transmission in Limp-in mode.

How does a mechanic diagnose the P0844 code?

Mechanics need an advanced scanner, a digital volt/ohmmeter, a manual pressure gauge, a hydraulic pressure diagram, and a manufacturer’s wiring diagram to correctly diagnose a P0844 trouble code. In addition to this equipment, the mechanic must perform the following steps:

  • Inspect the wiring, connectors, and components associated with the transmission, looking for any that have corrosion or damage.
  • The mechanic should also check the transmission fluid, looking for a burning odor or otherwise looking abnormal.
  • If this is the case, the mechanic should pull on the transmission pan and look for any signs of dirt, such as the clutch. This is an indicator that the transmission needs to be rebuilt and the torque converter replaced.
  • Once fixed, the mechanic should fill the transmission fluid to a level that will allow any leaks to be repaired.
  • After fixing all the leaks, the mechanic should fill the transmission fluid to a proper level. The mechanic should then clear the code, start the car, and allow it to come to normal operating temperature.
  • Test drive the vehicle to see if the transmission runs smoothly and if the trouble code returns.
  • If the trouble code reappears, connect the scanner to the diagnostic connector and download the stored trouble codes as well as freeze frame data.
  • Hook up a manual pressure pump to the transmission to check the hydraulic pump pressure. The mechanic should use a hydraulic pressure chart while doing this, comparing his findings to the manufacturer’s specifications. The mechanic should also test the electronic pressure regulator at this time.
  • Test the torque converter to see if it has gone bad.
  • If the code returns after clearing it, the mechanic should use a digital volt/ohmmeter to check the reference voltage and ground signal of the transmission fluid pressure sensor, electronic pressure control solenoid, and all related circuits. . If the voltage or ground is open, test the resistance and continuity of the circuits. The mechanic must first disconnect all related control modules to prevent damage to the controller.
  • Clear the code to see if it comes back. If so, check the PCM to see if it has gone bad.
  • Clear the codes one more time and retest the system to see if the code persists.

Common mistakes when diagnosing the P0844 code

Mechanics often mistakenly replace a high pressure pump in response to this code when the problem actually lies with the transmission pressure sensor, electronic pressure control solenoid, or faulty wiring. This misdiagnosis of the problem usually results in the code returning.

How serious is the P0844 code?

The severity of a P0844 trouble code can range from nothing serious to an inoperable vehicle not shifting properly, if at all. A driver of a vehicle that has a stored P0844 trouble code should diagnose and fix the problem as soon as possible to avoid potential problems.

What repairs can fix the P0844 code?

To repair a P0844 trouble code, the mechanic should do the following:

  • Replace any faulty or damaged wiring, connectors, or components.
  • Rebuild transmission ifit was damaged due to a low fluid level condition. The mechanic should also install a new torque converter when rebuilding the transmission.
  • Repair any leaks detected in the transmission.
  • Replace the hydraulic pump. The mechanic should note that this process requires removal and partial disassembly of the transmission, so plan accordingly.
  • Replace the torque converter if it is found to be faulty.
  • Replace the transmission fluid pressure sensor, electronic pressure regulator, or electronic pressure control solenoid if faulty.
  • Replace the PCM if it is damaged. The mechanic should note that PCM failure is rare and the component should only be replaced after everything else has been checked. PCM replacement also requires the mechanic to reprogram it.

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