If those sensors contain electronic components (which they probably do) resistance measurements can vary considerably,
depending on temp, type of meter used, etc. etc.

I suggest you check the ATF level with the car level, the engine running, and the ATF at about 35-40 degrees C.
ATF & Filter change. taligentx.com: Passat - ATF & Filter Replacement

 

Not intending to be the word police, but the correct term is "limp" mode, as in limping home from an injury. By the way, I don't think those speed sensors involve any electronics, they are probably simple inductive sensors like the ABS sensors or Engine speed sensor.

There is a useful PDF on the 5HP19, specifically the RWD version for a BMW, but probably relevant to the FWD versions as far as the electrical specs- search "BMW 5HP19 unofficial" which will lead to a bimmerfest.com article. This contains a chart of resistances for solenoids and sensors. There are also charts showing clutch and solenoid valve status for every gear. For instance, there is valve MV 1 which is ON for gears Reverse, Neutral, 1st, and 2nd, but off for 3rd. If for some reason this valve is stuck On, that might cause the incorrect gear ratio.

 

OOPS, limp. noted!

I am not sure what exactly is inside the sensors, they should be fairly simplistic but on the other hand it did make a difference of 1/3 of the value when i switched the meter leads / polarity. Maybe there is a diode or something in there??

The resistance chart is the exact same as in the document i used. It indicates Passat 96- up and my connector on the transmission has a slightly different shape than pictured (same number of pins though). Therefore i was hoping to see if anyone knows if the values are still the same in 2004/2005 or not...
The other charts are really interesting, thank you!

I'm going to check the fluid level this afternoon and report back. I will drop the pan this weekend, and then start ordering parts to put it back together. Are there any items besides the obvious filter, oil, gaskets and sensors that should be replaced?

 

Use a bit of Vaseline on the filter's seal, it will install much easier than trying to use ATF as a lubricant. I've always used Valvoline MaxLife synthetic ATF which you can buy in a gallon size.

As long as the pan is off, I'd consider removing that MV 1 solenoid valve to figure out if it is OK. The valve should switch On when 12VDC is applied. There may also be a small screen visible when that's removed, so check for obstructions.

 

I will keep that in mind when i drop the pan.

Ok, i checked the fluid - trans temp at 45 degrees C and after the initial 3-4 shot glasses the stream went to a slow but constant dribble. Fluid was still pretty red, as i expected since it was in there for just a few miles.

Since i had to run it to get to temp anyways, i checked the solenoids and regulators against the chart in the BMW document that was suggested earlier. This was done with the car on jack stands, wheels hanging freely, and i slowly accelerated until it reached 5th. No problems, no LIMP mode, the only thing i noticed was the shift to 3rd was a little less smooth compared to the rest.

I attached the chart with what VCDS blocks put out (X marks on, O marks off, numbers are mili amps). A few things did not line up:
-Solenoid 2 is ON in Park where chart says off
-Regulator EDS3 is ON in Park chart says off
-Regulator EDS4 is off in 3rd gear chart says on, but it depends on throttle position

Also, the speed sensors seemed to put out plausible signals, input sensor was on par with the engine speed and the output seemed to make sense too. I did not write down the readings of each gear to multiply them with the gear ratio and compare that to the input, but the output went up gradually and increased/decreased when the trans shifted.

After i was done, i re-checked the resistance of the speed sensors, both went up a little - i guess due to heat. I then did a test drive, because i did not get a single fault while on the jacks, which lasted 100 yards and i got the code for incorrect ratio in 2nd gear along with the limp mode.

So besides the findings on the solenoids (does that BMW chart apply 100% to an '05 Passat?!?) what can be the difference to make it work on jack stands but not on the road? Increased resistance/load on the trans from moving the car versus just the wheels? Can that cause the clutches to slip and throw the code??
:banghead:

 

A diode is an electronic device and can cause strange readings.

VW ATF is not red, does the ATF meet the VW/ZF specification ?

Have you checked the multi-function switch, wiring, connectors, and TCM ?

 

I still did not find the time to drop the pan yet, this thing called life keeps interfering lol..

The previous owner used a trans service kit from idparts.com , which contains Fuchs G052162A2 ATF.

I tried the MF switch, inspected the wiring harness, checked resistance values from TCM connector to the connector at the trans, checked the TCM for water or cold solder joints - all seemed fine.

In the meantime, i replaced the little magnet (was broken off) and now the tiptronic works again. During a test in manual mode it shifted fine from 1st to 2nd but then after a few seconds it went to 3rd followed by 4th right away without any input from my side.

Seems like everything is pointing to an internal failure...
At this point i am thinking about taking it apart to see what might be going on and maybe getting a donor V6 trans from a wrecked car to swap out what is broken inside mine. I read somewhere that the internal parts after the torque converter and before the final drive are the same.
Has anyone done this before? I'm aware that the inside looks like 10 pounds of s*** in a 5 pound bag...
I would prefer a manual, no question, but the electronic part of this swap (ECU...) is what scares me away from it and a professional swap would be more than the car's value.