Need Experienced advice on 41TE P0841
 

I have a 2005 Town and country, 3.8L, 41TE, 150k miles

Initial Symptoms:
- Starts in second gear
- TCC doesn't kick in
- I believe it originally had a P1776 (solenoid switch valve latched in LR position)

I did some research and used a diagnostic tree that pointed to replacing the valve body. I bought a used on from ebay which came from a vehicle with lower miles.

I did a little more research and found that the SSV wears and cocks sideways preventing the SSV from switching. I found that Sonex makes a SSV replacement that keeps that from happening so I ordered that too and replace the SSV in the ebay valve body before I put it on the vehicle just to avoid a future problem with the vehicle.

The original symptom of second gear start still was there, but now the code is P0841.

I decided to investigate the L/R pressure switch and back probed it and though it looked like the L/R switch was always low (key-on/engine off). I figured the switch was stuck on (low), so I replace the solenoid module with a new one. Turns out I didn't have a long enough back probe tip and missed contacting the connector only on that pin (2), but somehow manage to hit the others to make the comparison diagnostic. Darn Darn more frivolous expenses:mad:

So here's the part where it gets tricky.

I monitored the L/R pressure switch with a volt meter while I shifted through the gears. The fluid diagrams indicate there should be L/R pressure in Neutral and First. But by indication of the new solenoid module L/R pressure switch (pin 2) going low on my volt meter, there is L/R pressure only in Reverse.

It pretty much takes a rocket scientist to fully understand the fluid diagrams, but the part I'm not sure about is how the L/R pressure switch is getting activated in Reverse since it looks like the only way to get pressure on that circuit is from the LR/CC solenoid. The solenoid is controlled by the TCM and I have to assume that there isn't anything wrong with that circuit meaning it's not shorted high or low, because either I'd see pressure at Neutral if the SSV was correct, or if it wasn't the TCC would be locking in all the forward gears. Correct?

I don't want to start shotgunning expensive parts into this vehicle unless I understand exactly why.

I'm stumped...Help!

Oh, here's one more piece of data. If I'm driving and come to a stop light and put it into neutral then put it into drive when the light turns green it'll start in first gear. But if i'm backing up and stop just long enough to switch to drive it also starts in first for about two seconds then pops up to second with a bump...WTF.

Any ideas....anyone...:confused:

In case anyone was curious to know what the real problem was, I just had to sleep on it overnight to figure it out.

Turns out in a hast to figure it out I had got caught in the inverted logic of the L/R pressure switch. This morning I realized what I had done and that 12V was really off, duh. The fluid diagrams did match what my tranny was doing. I think I even wrote it wrong in my previous explanation. I said it correctly when explaining how the switch logic worked, but when I was monitoring it on the car I didn't think hard enough and when I saw it go from 0V to 12V I assumed that was pressure and forgot about the reverse logic.

Once I got regrouped I realized it had to be a connection between the solenoid module and the TCM.

Didn't take long to find the opened wire (see pic). The wire was on the outside of the bundle and rubbed against an inside corner of the back cover of the connector. From the looks of the amount of corrosion when I stripped it back it must have been that way for some time. I just bought the vehicle and can't believe what some people just live with.

Now all I have to do is replace the engine with a rebuilt one. I managed to buy the year vehicle (2005) when they built the 3.8L with insufficient oil galleries. It has the funny mis on cylinder #2 which is most likely the cam lob wearing off from insufficient lubrication. I can feel the roughness in the rocker arm of the cam roller on the cam, just by touching the rocker with my finger.

I could have probably just turned around and resold it right away since I got a pretty good deal on it, but I couldn't get myself to morally sell it to anyone since it would probably have been some soccer mom.

I can't trust it now to take any trips, but it should be a pretty good vehicle after I switch the engine.

Anyone know for sure if the engine can be taken out the top. I've seen a couple dialogs where they said that's even the best way from some experienced garage guys, which say it is even quicker. Just have to remove the windshield wiper stuff.

Later,

K

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