Here's 01m part 4
I've been meaning to post this info in much more complete format, but this info seems needed and I'm typing much of this info in tech help emails, and on the forums, or explaining it on the phone, so I'm gonna just post up what I can quickly, and reserve space for future additions when I have time.
A lot of this info is applicable to any solenoid. For instance EGR or Boost solenoids, or gasser injectors or maybe even applicable to a certain extent to diesel injectors on BRM and BEW. You just need to understand that air or gasoline is a fluid just the same as trans fluid.
A solenoid is a electomagnetic-hydraulic device to that electricty can be used to control fluid. Transmission solenoids have a specific funtion. To allow the computer to control movement of valve.
If you take apart a solenoid you would find a "winding" and a "pintle". When amperage is flowing through the windings it makes a magnetic field to move the pintle. The pintle is a a small valve that either blocks fluid pressure or vents it.
Electrical issues with solenoid.
If you have a solenoid code
then you may have a electrical problem with the solenoid. There are various methods that car designers can use for the computer to "see" a problem with the solenoid. These methods would include the computer actually measuring the amperage flowing through the solenoid circuit, voltage checks on the solenoid circuit, and the computer looking for a inductive spike when the solenoid is shut off. I don't know which method VW uses because Vw doesn't publish this info, but its irrelevant anyway. I do know this, VW's trans computers are real good at "seeing" a problem with the solenoid circuit. So if you don't have a solenoid code then you don't have an electrical problem with your solenoid, so put away your ohm meter and look elsewhere. Ohm checking when you don't have a solenoid code is a complete waste of time.
Now, you have to understand that the computer has no way of knowing if the problem with the circuit is actually the solenoid or the wiring between the computer and the solenoid. Problems like mouse chewed wires, corrosion in TCM connector, water in the solenoid connector, open circuit in the internal harness, bad power or ground to the trans computer or bad trans computer can cause these codes as well.
Diagnosing a solenoid code.
Diagnosing a solenoid code is real easy! As long as it's reoccuring immediately and consistently. If its not reoccurring consistently it can be just short of impossible.
Reoccurring immediately and consistently is defined as, "you clear the trans code with vag-com and the code comes right back every time". This usually means you have a open or short in the circuit and should be easy to identify with an ohm meter. I'm not going to explain how to use an ohmmeter but techniques include....
1. Removing the pan & ohm checking the solenoids. Drawback of this is it requires pulling the pan and this check doesn't check the integrity of the internal harness.
2. Ohm checking through the solenoid and harness from the computer with the computer unplugged. Drawbacks of this is that it requires a wire schematic and its hard to get to the computer. Benefits is you can identify problems in the harness.
3 . Ohm checking through the solenoid and internal harness from the trans connector. Due to difficulty in pulling the trans computer and not wanting to pull the pan, this is where I would normally start on a 01m.
Use the info from my website to know solenoid connector pinout for ohm checking at this link
Here's more info on this process and using the solenoid connector pinout from the link above.
every solenoid has 2 prongs. One for power and one for ground. To ohm check a solenoid at the solenoid, you would put you muliti-meter on the ohms setting, with one lead on power (one prong), and one lead on the ground (other prong). But this would require pulling the pan and it doesn't check continuity of the internal harness. So to ohm check the solenoid through the harness you do the same thing just through the harness.
Pin 2 on the solenoid case connector supplies power (voltage supply)
to the EPC solenoid. It says voltage supply on the chart.
So if you were checking the EPC solenoid resistance through the case connector you would put a lead on power to EPC solenoid (pin 2) and the other lead on the ground to the EPC solenoid (pin 8).
All the other solenoids use pin 1 as power (voltage supply)
so for to ohm check all the other solenoids you put one lead on pin 1 and the other lead on the pin that corresponds to a specific solenoid ground.
Now that I've used the term "ground" someone is gonna say "my harness isn't showing ground right now as I check it". Of course it isn't. These solenoids are provided with power all the time and when the computer wants them on, it grounds the solenoid. When the computer is commanding the solenoid on is the only time you will see ground on those wires.
Note: intermittent solenoid codes are difficult to impossible to pinpoint using ohm checks!
I would suggest if you don't have an ohm meter, or have lots of questions or don't understand this then you should just buy a solenoid and try it. Usually a solenoid code is caused by the solenoid except for the things listed above.
Solenoid position on the valve body is as follows.
2 N89 energized in 2nd and 4th to apply b2 brake
1 n88 feeds k1 clutch and b1 brake
5 n92 energized on each shift to cushion shifts
3 n90 feeds k3 clutch
4 n91 TCC solenoid
6 n93 pressure control solenoid
7 n94 controls apply to b2 brake
n89, n88, n94, n92 and n90 should ohm check at 55-65 ohms
n91 and n93 should ohm check at 4.5-5.1 ohms.
4-2-2013 Edit: N91 and n93 are fatter and cant be installed in the wrong location. Others are smaller and could potentially be installed in n91 or n93 spot. If you put the high resistance solenoid where the low resistance solenoid goes it will cause failsafe with a solenoid trouble code.
When the solenoid code is not reoccuring consistently it is very difficult to pinpoint the cause.
Intermittent code is defined as... You're driving along and the code triggers. You clear it and it doesn't reoccur for "some interval of time". IE till the next day, or till the next week, or 2 weeks later. You would have to do your ohm checks at the immediate moment that the code reoccurs in order to pinpoint the problem. Lots of times in these circumstances it is the winding in the solenoid shorting to itself effectively shortening the length of the winding which changes the resistance of the solenoid. Sometimes the windings can short for just brief intervals and then not short again till its hot or till some random bump in the road or just plain intermittently. Other times you might have a bare spot in a wire rubbing something and shorting to ground sometimes, or you could have a intermittent "open" in the internal harness or things like this.
If you have a intermittent solenoid code you should do a good visual inspection of the harness between the trans and the computer unplugging and inspecting all the connections, and if you see nothing then try a solenoid.
If I were involved in a intermittent solenoid code and the solenoid didn't fix it, and I found nothing in the other checks then I would attach a 2 channel scope to power and ground on the solenoid and drive it till it acts up.
Note: intermittent solenoid codes are commonly caused by water in the solenoid connector on top of the trans. If it happens when its raining or after driving through a puddle then open the connector and blow it out with compressed air or brake clean, clear the code and see if it reoccurs.
NOTE: Sometimes solenoid codes or other codes on a 01m do not clear on their own even if you have fixed the problem. In these circumstances you will have to clear them with vag-com. OBDII may work also.
Mechanical issues with solenoid (sticking solenoid).
The electrical portion of the solenoid makes a magnetic feild to move the "pintle". The pintle needs to move freely. Fluid pressure is routed to the solenoid and the pintle either exhausts the pressure, or blocks the pressure. That pressure is used to move a valve. If the pintle sticks, it can block the pressure when it should be exhausting the pressure (stuck on) or it can exhaust the pressure when it should be blocking it (stuck off).
The first thing you need to do if you suspect a sticking solenoid is PUT YOUR OHM METER AWAY! You cannot determine that you have a sticking solenoid by ohm checking!
The pintle being stuck doesn't affect the resistance of the solenoid in any way, shape or form.
There are three ways to determine a sticking solenoid.
.The best way to find a sticking solenoid is to understand each solenoid's function. See my website in the 01m FAQ for solenoid function.
stuck solenoid example 1
N89 stuck off...
The n89 solenoid turns on the B2 clutch and is on in 2nd and 4th. So if you drive the car and it shifts 1-3 with no 2nd and 4th you might assume the n89 is stuck off. The complicating factor here is you could also have the B2 clutch inop and it might behave this way also.
N89 stuck on...
Lets say you drive the car and it starts in 2nd when it should be in 1st and does nothing when it should change to 2nd, and shifts to 4th when it should shift to 3rd then you could assume the solenoid is stuck on.
stuck solenoid example 2
Engine dies when you place it in gear. You could assume the torque converter clutch solenoid (n91) is stuck on.
Or if the Torque converter clutch was not working you could assume the n91 solenoid is stuck in the off position. Unfortunately, the torque converter clutch not working is most commonly caused by wear in the a valve body, but certainly you can try the solenoid first if you have this problem.
stuck solenoid example 3
The n93 solenoid controls pressure. This pressure can be easily monitored on a pressure gauge hooked into the tap on the trans. If the n93 were to stick in the high pressure position you would see it was high on the gauge it would cause harsh shifts. If the n93 were to stick in the low pressure position you could see it on the gauge, and it would be too soft shifts and would probably burn up the trans very rapidly.
I get lots of emails saying "how do I tell if its the solenoid" and I refer them to this thread. But they still want more info. Alot of times I say, "you sometimes just have to try it" if you think you have a sticking solenoid, but they will want some "easy test" to know whether its the solenoid or not. Well it just aint that easy. The following is "the advanced method" for seeing if a specific solenoid is stuck.
Advanced Solenoid Diagnosis"
First of all you would have to have a theory on which solenoid is stuck. You would get this theory by knowing the solenoids functions and theorizing which one might be sticking "laymens method" from above. Then you would have to own an oscilloscope and a inductive amp clamp. And of course you would have to know how to use it.
You get out your wiring schematic, find either a ground wire or power wire to a specific solenoid that has no other activity on it. It would be preferred to do this test while driving the car using the solenoid "in operation". But if you cant do this then you could do it with jumper wires. Jumper wires isn't as good of a check though because a solenoid can stick intermittently, and if your driving the car you can know when its sticking and when its not.
Ok so you clamp the power or ground wire. your set up the scope, and then drive the car or cycle the solenoid with your jumper wire, and this is what you should see.
Now unfortunately this isn't a 01m solenoid, the transmission was a GM 4t65E that comes in Impalas, monte carlos and other GM front wheel drive cars, but the principal is the same. There will be some differences especially in the amount of amperage that the solenoid will draw, but all solenoids will behave this way, including EGR solenoids, boost solenoids, EVAP solenoids, transmission solenoids and most injectors.
Here is a amp pattern of a stuck solenoid. Same transmission as from above.
Now there is a very minor inductive "hump" in the ramp but not enough to show the "pintle" moving. The 1st currant ramp picture was actually taken after replacing the stuck solenoid. Disregard the differences in the "scale" of the picture as I had the settings different. The amp draw is irrelevant anyway as the only thing your concerned with is the "inductive hump". If you had a solenoid trouble code you might be concerned with amp draw but the only time you would go this far with a solenoid diagnosis is if it was a intermittent problem.
Please don't ask me if there is an easier way, or if there is a way that you can tell without owning a 2000 dollar oscilloscope. Also don't ask if you can do this by checking amperage with a DVOM, cuz you cant.
Now I have to say that I do this check very infrequently as I use the "laymens method" described above. I used the inductive amp clamp on a scope technique on this 4T65E transmission because if you want to "try replacing the solenoid" on the 4t65E then you have to pull the subframe and, pull the side cover which is no easy task. So on this one I wanted to be absolutely sure. Usually to do this check, by the time you look up the schematic, find a good place to put your amp clamp, hook up the scope and make the decision, you could have all ready changed the solenoid on the 01m.
3rd method "Musical solenoids"
So if your thinking you have sticky solenoid and the "laymens method" above isn't clear, then you can do what I do sometimes and I've come to call it "musical solenoids" (think musical chairs). You simply pull the pan, and move each solenoid to a different location. Keep track of how you move them so you can know and evaluate the problem based on the way the trans works with the "suspect" solenoid in its 2nd location vs in its 1st location.
But thats a whole lot of work you say?... so what? Its free! Just drain the oil into a container, reuse the filter and pan gasket, and dump the original fluid back in. Or you can use this as a good time to change the fluid. Seems everyone thinks changing fluid might fix their problem (wishful thinking) so as soon as they notice anything their knee-jerk reaction is to change the fluid. I'm ok with this as long as you inspect the bottom of the pan with a flashlight and break open the filter looking for metal.
If you don't like the amount of work that Musical solenoids entails then you can certainly do "advanced solenoid diagnosis" or run up to your local dealer and pay their diagnosis fee to tell you it needs a trans (whether it does or not).
So in review... its just not easy. It takes lots of specialized knowledge (operation of the solenoids, how to use a scope, how to read wiring schematics) and some special tools (scope with amp clamp). Even when the cars are here sometimes you just have to try it to see. Sometimes it will fix it but sometimes not.
Replacing transmission solenoids in a 01m.
I get asked this a lot. The main thing you need to know on a 01m is that YOU DON'T NEED TO PULL THE VALVE BODY TO CHANGE YOUR SOLENOIDS". I get an email with this question at least once a week.
Changing 01m solenoids is super easy and on most cars (with missing belly pan) I can change them lightning fast. But most people are going to want to do the correct check procedure and that requires some method of checking temperature so you'll need vagcom.
Definition of terms.
1. Valve -- NOT A SOLENOID. The term solenoid valve although true in the most literal sense is confusing. I just want to differentiate that a valve is not the same thing as a solenoid. It would probably be best to call a solenoid a solenoid and not a solenoid valve.
2. Solenoid-- electomagnetic-hydraulic device so that electricty can be used to control fluid.
3. Fluid-- AIR, vacuum, or liquid.