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 (solenoid codes) .
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.
Lots of aftermarket sources define P0740 as TCC solenoid circuit (or similar definition). But, P0740 is NOT a solenoid code. Vagcom and other correct information sources define it as "Excess TCC slip" See 01m part 3. Dont try to diagnose P0740 as if it is a solenoid code. IT IS NOT A SOLENOID CODE. P0740 might be caused by the solenoid in some rare instances where the solenoid is stuck off, so see the section in this thread about "mechanical issues with solenoids". A stuck solenoid will not trigger a "solenoid code". A solenoid code is a problem with the electrical circuit relating to the solenoid, and a stuck solenoid will NOT affect the electrical portion of the solenoid. Please note: If your solenoid is sticking off it can cause P0740 but usually it will stick off sometimes and stick on sometimes. The symptoms for sticking on are so Radical and undeniable that you would never be concerned with the TCC stuck off. See stuck solenoid example #2 in the "mechanical issues with solenoid" section (post #2).
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 solenoid code with vag-com or your OBDII code checker and the code comes right back every time". If the solenoid code reoccurs immediately and consistently this usually means you have a open or short in the circuit and should be easy to identify with an ohm meter.
Please note: some transmission codes will put your 01m in failsafe or limp mode, and do not "reset" or clear, even if the problem is not currently evident or even if the problem has been repaired. You MUST clear these codes. If you repair a problem, and you are still in limp mode (failsafe) then you MUST clear the codes as repairing the problem will not take it out of limp mode. Maybe with enough driving or enough key resets it would but it would be better just to spin over to your local buddy with a code checker and have him clear it. Just because your transmission is in limp mode does NOT mean the problem is reoccuring. Limp mode is not your problem, Limp mode is the computers reaction to the problem. People always say, "yeah its doing it consistantly! Its doing it right now." Just because its in limp mode does NOT mean the code is reoccurring immediately and consistently.
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 following pic to know where to ohm check.
Of course here is my website for more info.
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.
MULTIPLE SOLENOID CODES on 01m
Lots of times folks will contact me and have multiple solenoid codes and want to know what to do.
1st. Understand that most of the solenoids in a 01m are powered from the same wire. They get this power from the computer and it has to pass through the cars harness and reach the solenoid connector. Then this power has to make it through the internal harness to each of the solenoids. Heres a diagram of the internal wiring to the solenoids. This is the diagram for a older jetta so it might not be exactly the same for all cars but the logic applies.
As you can see the last wire on the right powers all of the solenoids except for the #6 solenoid. So logic would say if you have a code for all the solenoids except for #6 then you would have a break in the harness of the car or a break in the internal harness before the solenoids.
Or if you had a code for all the 1-5 solenoids then logic might say that you have a break in the internal harness after the bridge to the 7 solenoid but before the 1-5 solenoids.
But there is a problem with this logic. The computer will sometimes only trigger codes for the solenoids that are on. If the trans went to failsafe before the codes triggered then it might not have triggered all the codes even though there is no power to them. Sometimes the computer isn't so great at giving the best info with multiple codes.
So what you have to do when you have Multiple solenoids codes is realize that most likely 4 or 5 solenoids didn't all fail at the same time. Its likely that a group of solenoids lost power at the same time.
First check that you have 12V at the solenoid connector on top of the trans. See my website (linked above) to know where the solenoid connector is and check the diagram above to see where to check for !2 V. If you have 12V on the power wire then you should ohm check through the solenoid connector for all the solenoids. If you have multiple soelnoids that read open checked this way then in all likelihood you have an open in the internal harness and your next step would be to pull the pan and unplug the solenoids and do ohm checks of the harness itself.
And of course dont forget that your computer must be powered up with 12V and have good ground to it as well. All the things I mentioned above can still be the cause of multiple solenoids codes (computer, car harness, trans internal harness, water in connector ect).
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.