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Transmission Pressure Control Solenoid

Transmission Pressure Control Solenoid

The transmission pressure control solenoid is one of the automatic transmission’s many critical components. While a clutch controls when and how gears shift in a manual transmission, solenoids are part of an automatic transmission’s complex hydraulic system that does the same task. 

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They are also electro-hydraulic valves that control the flow of transmission fluid throughout the transmission. They open and close according to the electrical signals they receive from the vehicle’s engine or transmission control unit. They work based on data from a series of speed sensors located in the engine.

 

A transmission PCS is needed for the transmission not to seize up from lack of fluid or to bog down as a result of too much fluid. There are different types of solenoids, namely: transmission shift solenoid, the lockup solenoid, and the transmission control solenoid. 

 

Transmission shift solenoid – is responsible for controlling the flow of transmission fluid. It receives electrical signals from the transmission control module (TCM) telling it when to transfer fluid into and out of the transmission and at what rate. The shift solenoid’s role varies depending on whether the vehicle has manual, CVT, or manual transmission.

 

The lockup solenoid -It's an electrically operated valve in an automatic transmission, which is controlled by the car's computer. When the computer sees it effective to lock the torque converter up solid, the solenoid is powered to make the transmission lock up.

Where is the transmission pressure control solenoid located?

The solenoid operates through signals or voltage supplied by the electronic control module or transmission computer. They are usually located within the valve body, the transmission control module, or the transmission control unit. In most cases, solenoids are installed inside of the oil pan, connected to the valve body of the transmission.

Transmission Pressure Control Solenoid Symptoms

  • Performing Erratically

 

One of the most common symptoms of a failed or failing transmission pressure control solenoid is when your automatic transmission performs erratically like a car jumping to another gear while driving.

 

A transmission pressure control solenoid that is failing can cause slipping in one or all gears. These uncontrolled shifts come as a result of solenoids opening or closing without having received any signal that should have come from the transmission computer. This is often caused by bad wiring within the solenoid. 

 

When the transmission control unit in the engine sends signals to the solenoids to shift up or down, the valves open or close to allow or restrict the flow of transmission fluid that pressurizes the transmission’s clutches and bands. This mechanism allows the car to change gears.

 

The uncontrolled opening and closing of solenoids may also come as a result of physical breakdowns making it difficult for the solenoid to maintain proper positioning, either open or closed. 

 

These unwarranted gear shifts may take place in either direction. The car may randomly jump to the next lowest gear, causing the RPM to suddenly spike or  jump to a higher gear resulting in the car stalling out. If left unrepaired, the friction from the slipping can end up frying the clutches and bands causing the transmission to eventually fail. 

 

To state that the lockup torque converter can lock the engine and transmission together also isn’t entirely accurate since shifting can still happen if the vehicle has a heavy enough load. When a transmission slips while in lockup because the system is overloaded it will generate tremendous heat leading to transmission failure.

 

In this case, it is very important to seek the intervention of a transmission professional as soon as possible. The sudden shifts or slips will not only be stressful but also can put the driver and/or the passengers in a potentially dangerous situation.

  • Delays In Shifting

 

Changes in the internal pressure of the transmission are what allows the transmission of a vehicle to move from gear to gear. The pressure changes being made possible by the movement of the solenoids. But as transmission pressure control solenoid ages, and begins to wear out, it will also display a noticeable lag in carrying out the instructions allowing the transmission to shift from gear to gear. 

 

This could result in noticeable disconcerting “gaps” between one gear and another and could even feel like your vehicle has lost its power completely at such times, as the sluggish solenoids struggle to get into their new positions.

  • Inability to Downshift

 

Another common sign of a faulty solenoid is a transmission that is able to move smoothly upward from gear to gear but cannot shift back down. In short, you will notice odd behavior only when decelerating, and not while accelerating.

 

This happens when a solenoid has become stuck in an open orientation. This can be a result of physical damage to the solenoid body or a result of bad wiring that is preventing the solenoid from receiving the electrical signals. Another reason could be an obstruction or foreign matter that is preventing the solenoid from shifting into position. This often comes as a result of dirty transmission fluid.

  • Illuminating Check Engine Light

 

Do not be deceived as the absence of all the symptoms above is not an assurance that everything is okay. Sometimes a sign of a problematic transmission pressure control solenoid is also an illuminating check engine light with little to no other symptoms.

 

A bad transmission solenoid will set a diagnostic trouble code (DTC),  causing the check engine light to illuminate.  In this case, an On-board Diagnostics OBD-II scan of your car’s computer will give information indicating a faulty solenoid. The DTC explanation will indicate that the issue may be an open circuit in the electrical system of the transmission.  So always check the solenoid to verify its condition before replacing it. DTC has codes specific to transmissions and solenoids.

How to Test Transmission Pressure Control Solenoid

 

The shape and variety of solenoids found in modern transmissions change with every new car model. In every rebuild, the solenoids should either be verified or tested for proper operation or replacement. Some mechanics choose to just replace all the solenoids on the valve body. That only makes sense as the replacement solenoids on some car models are fairly cheap. But for other models, the solenoids can be expensive so it makes it worthwhile to test and replace only the ones that are worn or faulty.

 

When you want to test a solenoid, do it with a hydraulic solenoid testing machine with specific adapters for each solenoid because it is by far the most accurate way to do the testing. And you don’t have to worry about how to go about it as most of these machines come with documentation to guide you through the whole testing process.

 

Once you are able to diagnose a failed transmission pressure control solenoid, it must be replaced as soon as possible. The replacement of a transmission pressure control solenoid can be done by most automobile dealership service centers, any auto repair shop, or you can even do a do-it-yourself “DIY.”

 

How do you change a transmission pressure control solenoid?

 

The transmission pressure control solenoid is found on the body of the transmission and removing and replacing it will not be very difficult. The challenge will be locating and identifying the pressure control solenoid as there are other solenoids in the same general area. Here are the steps in removing and replacing a transmission pressure control solenoid.

 

  1. Remove the battery from the device. Remove the negative terminal first, then the positive cable, using a socket set and wrench. Remove the dipstick from the transmission while standing over the engine bay and with your tools, slide under the vehicle. Position an oil pan underneath the transmission. To drain the oil into the tub, unscrew the fluid plug on the bottom of the transmission.

 

  1. Carefully remove the oil pan under the transmission. Remove some 20 bolts or so with a socket wrench and place them on the oil pan so won’t sully them with dirt by laying them on the ground. The transmission fluid will help keep them clean and lubricated. Peel off the gasket from the rim of the transmission fluid pan as it sticks to one or the other.

 

  1. Remove the fix plate by unthreading the bolts or screws. The transmission parts diagram can be found in the vehicle owner's manual. Determine the transmission pressure control solenoid. Remove the two wires from the solenoid and the patch plate. The transmission pressure control solenoid is attached to the repair plate with tabs that must be depressed before removing it or small screws that must be unthreaded first.

 

  1. Fix the new transmission pressure control solenoid in place and connect the two wires to the appropriate terminal tabs. Replacing the repair plate is a simple matter of tightening the screws. Apply transmission fluid to the new gasket and wrap it around the oil pan's bottom. Place the oil pan under the transmission and secure it with bolts. Refill the transmission fluid. The correct sum is stated in the owner's manual.

 

Transmission Pressure Control Solenoid: Replacement Cost

 

The cost of replacing a bad transmission pressure control solenoid varies by car make, model, and year.  Other factors that also influence the cost also include who will do the work, like if it will be an auto repair shop, a car dealership, or if you will do-it-yourself. If you decide to do it yourself, where you decide to purchase the replacement solenoid will also influence the price.

 

On average, replacing the solenoid in your transmission will cost anywhere between $150 and $400. The labor, which should take 2 to  4 hours will cost around $60-$100 per hour. The parts can cost as little as $15 or as much as $100 for every solenoid.

 

Transmission Pressure Control Solenoid: Other Frequently Asked Questions

Can I drive with a bad solenoid?

 

The answer to that important question is yes. You will still be able to usually drive a vehicle with a bad solenoid given it might not shift past a specific gear. You will still be able to drive it for a short period of time without causing any serious damage. 

 

The fluid pressure control will still be able to continue to function in the gear with a functioning solenoid, but putting any serious stress on the transmission like carrying a heavy load or drag racing should be avoided. All of this is under the assumption that your particular transmission doesn't use a solenoid to engage the first gear, as well as the first gear solenoid, didn't go bad. But if it did go bad, then you will know right away because the car wouldn't move.

How do you fix a stuck transmission solenoid?

 

A stuck transmission pressure control solenoid will cause difficulties while shifting gears or worse complete inability to shift gears. You might be annoyed and start trying to force the vehicle into gear,  but best to stop it as you might just end up with even more damage to your transmission. To avoid any such condition the issue should be addressed as soon as possible. Following these repairs and replacements steps may help you to fix the issue of a stuck transmission solenoid. 

 

  • Inspect the transmission filter carefully and replace it if you see that it is clogged or broken.
  • Replace the shift solenoid that has gone bad.
  • Also inspect the level of your vehicle’s transmission fluid and refill it if it needs to be topped up.
  • Change the transmission fluid if you see that it is already dirty or has been contaminated.
  • Replace or repair the worn-out wiring and connectors.
  • Replace or repair the faulty transmission Powertrain Control Module (PCM).

 

Next to a vehicle's engine, the transmission is one of the most important and expensive internal components. With that, it is wise and important to be educated of the signs that something may be wrong with your transmission pressure control solenoids. Again, it is not only a matter of replacing it for stress-free driving but also for safe driving.