Automatic Transmission Pressure Control Solenoids Operation and Testing

[@davidrioux611]

Is the Pico scope a Brand of manufacture of a scope? If I read the title on your page it may be a model/ version 7? Is it a independent instrument or an accessory that can be used with a particular scan tool or even multiple scan tools from different manufacturers? That display page is fantastic. Does the tool use a pc ( personal computer) and software to view data or are we looking at a screen shot from a stand alone tool that was uploaded to your video? I have a Fluke automotive meter with an induction clamp. Set of pressure gauges. I’ve found other alternatives for diagnosis. Using a scope is great but it is specific and therefore usually not used often. Maybe I would use it more often if I had one?

[@davidrioux611]

Good video

[@DrivelineMaster]

Thanks for your comment and questions. Pico is a brand and Pico Scope Version 7 is the version of software that interfaces with the scope. Pico offers PC and MAC versions of their software. The software is free and they have a demo mode so a user can learn before purchasing the Pico Scope hardware. Pico has different hardware models with various features or capabilities. The most current is model 4425A. You can learn more at: www.picoauto.com/. If your just getting into scopes you may want to consider a simpler less expensive one channel scope. I have a whole series on the uScope by AESWave on how to use this powerful little one channel scope. kzbin.info/www/bejne/q5TXlaqChqqambcsi=RCBXy4DAaK5QlCFe The uScope not as robust but it has some great features, advantages and capabilities. There is a ton more you can do with any scope verses a DMM. Information on most digital scopes are updated millions of times a second verses your fluke that updates 4 - 5 times a second. A quick example would be to measure the duty cycled voltage from a computer to a solenoid. You won't see the full 12V but a scope will display that as a square waveform showing the full 12V when the solenoid is on and a full 0V when it's off. The Fluke will average the on and off times to display partial voltage based upon the duty cycle percentage. Techs that I know that have learned to use a scope during diagnosis know when to grab their scope over their Fluke because diagnosis will be faster and more accurate. Also to your question the Pico is a stand alone tool that has nothing to do with your scan tool.

[@craigbaggett3370]

How often should you change your pressure solenoid to make sure it doesn’t fail

[@DrivelineMaster]

PC solenoids are not a maintenance item. The best thing you can do for your solenoid and transmission is to change the fluid and normally I recommend doing this sooner than what the manufacture recommends. It also depends of if the fluid is just a drain and fill or a complete fluid exchange. If the transmission does fail and has to be rebuilt I do recommend replacing the PC solenoid at this time.

[@brettgooseauto4390]

Thanks, once again.

[@sivucit]

Hi Is pressure control solenoid and pressure sensor(honda which uses to check the pressure applied on clutch that act as feedback to TCM) to adjust the pressure ).. are both same.. 2. what is the difference between line pressure control solenoid and shift solenoid. 3. Does CVT have same kind of solenoid like pressure control and shift solenoid.? Thanks much in advvance.

[@DrivelineMaster]

A pressure control solenoid is controlled by the TCM. The TCM sends a duty cycle signal to the PC solenoid to control the pressure in the circuit. A sensor is a TCM input. the sensor reports to the TCM if there is pressure and how much it is. The TCM could use this to change the PC solenoid Duty but not always. it could just be used to confirm that pressure is present in that part of the circuit. PC solenoids are always linear meaning it's controlled with a duty cycle to change amperage flow. It's not normally fully open or closed but always changing someplace in-between. Shift solenoids can be linear or simply on or off meaning fully open or fully closed. Simple on/off solenoids are either 100% open or 100% closed and nothing in-between. Yes, CVT's will also use various types of solenoids to control various operations. They would not be shift solenoids because CVT's don't produce step shifts.

[@sivucit]

@@DrivelineMaster thanks. Can I assume shift solenoid is used to change or shift gear and pressure control solenoid is used to help maintain pressure that helps shift solenoid to shift properly. Trying to understand relationship between pressure solenoid and shift solenoid paternship.also for Camry is pressure sensor not pressure control solenoid is in valve body. In Honda pressure sensor is outside

[@DrivelineMaster]

Shift solenoids are used to change gear ratios and pressure control solenoids are used to control the fluid pressure. I would not use the word maintain but instead I use control because the pressure varies depending on the engine and transmission load. More throttle = more engine load which = more pressure. The fluid pressure flow through a circuit is controlled by the shift solenoid. Think of a shift solenoid like the fixture at the end of your garden hose. You pull the lever and water comes out. you let go of the lever and water stops. That would be an on/off solenoid. If however you pull the lever 30%, 50% or 70% of the way open water comes out proportionally. That would be a linear or duty cycled shift solenoid. So the PC solenoid doesn't help the shift solenoid it just makes sure the proper fluid pressure is ready and available to pass through the shift solenoid. For your second question about the pressure sensor. Back to the garden hose. Lets say you disconnect the garden hose at the hose bib and you connect a water pressure gauge to the bib and the garden hose to the other end of the gauge. The water can flow through the gauge and provide you with the amount of pressure but it can also let the water through to your garden hose. As you are using the garden hose you can also observe how much pressure you have. The pressure sensor is the gauge except the gauge reports to you by showing you how much pressure there is. it's visual that you see with your eye. The pressure sensor reports to the TCM only its in the form of a voltage value that the TCM can interpret and translate into pressure. It doesn't matter what year and make of the vehicle the engineers know where the fluid passages are (hose bibs) and they decide where to put the pressure sensors. Sometimes it's inside the transmission in the housing or on the valve body or sometimes its on the outside of the transmission. Which ever is the most cost effective during production.

[@sivucit]

@@DrivelineMaster thanks so much. You are a master in explaining things. Will there be a case where line pressure solenoid shows correct pressure and shift solenoid is good but there is still a problem in transmission on a specific gear?. I am trying to understand the testing part. Manual says to tap the line pressure and find the psi at various speed, if pressure is bad it points to possible cause. Question is if line pressure is good will there be case where I still have to open transmission. ? Or will the line pressure helps me any way to decide if I can fix without opening transmission

[@DrivelineMaster]

The line pressure solenoid doesn't really show what the pressure is. The line pressure solenoid will display on the scan tool in amperage. High amperage around 1.0 amp = low pressure and low amps around 0.3 amps = high pressure. An increase in engine load should cause the amperage to drop which = higher pressure. If the scan tool is providing you with a line pressure value in PSI or Kpa this is coming from a pressure sensor that is taped into the line pressure port. Often pressure testing a system like this is done by putting a pressure gauge in the line pressure test port and comparing the amperage on a scan tool to the actual pressure on the gauge. You can also try using the PSI value in the scan tool if it's available but I prefer a real gauge or pressure transducer and a scope if you have one. Scan tools sometimes have active test that will allow you to control the amperage to the PC solenoid. Doing so allows you to set a specific amperage to compare to the gauge pressure and then compare the pressure and amperage correlation to the chart in the manual. Line pressure is not everything but it's the heart of the transmission operation just like your blood pressure is to the function of your body. The first thing the doctor does when you have a complaint is take your blood pressure. If the line pressure is within the proper operating range there are a lot of other things that can cause transmission shift and gear ratio problem. Shift solenoids, sticking or leaking valves in the valve body, speed sensors, governor sensors, TCM commands, grounds and wiring inside and outside the transmission, hard part failure etc.. Just like a good blood pressure can't tell you that you that the pain in your ankle is because you sprained it when you twisted it yesterday. Pressure is jut another diagnostic bit of information to help the technician narrow down the cause for the symptom.

[@Hurlburton]

Good class