2009 Saturn Outlook *stuck in limp mode

165,xxx miles

This car has been intermittently going in and out of limp mode since I got it. Usually when you pull over, turn the car off and sit a few minutes it works fine again after restarting. Well, here a few days ago trying to leave work it stayed in limp mode for good. Coincidently this is the exact same time my fuel gauge started going wonky (moving up and down the entire length of the gauge while driving). I took it to a mechanic yesterday and talked to them this morning. The lady on the phone started reading off codes and said it needed a fuel sending unit (no surprise there), purge valve (again no surprise, I've been having issues starting after getting gas) but the main course was when she told me transmission control solenoid it needed a TCM and quoted me $2200.

My initial instinct was to just go ahead and have them fix the sending unit and I'll replace the valve myself then get a second opinion somewhere else until they told me that would cost over $300.

I have this feeling (and it is just a feeling) that they just read off codes and made the call based on that. When I brought the car in the lot was full and they seemed really busy. I didn't know until today they had made the call the same day I brought it in. Damn that was fast.

Needless to say this is very disappointing news. Other than the limp mode the transmission has been working butter smooth. I've checked the dipstick several times before and the level was fine and clean. I'm scheduled to take the car in to another shop first thing next week to get a second opinion about it. Is this a reasonable reaction? Did they make a reasonable call?

EDIT: Just thought I'd add something, probably not related. I've had this car for two years and I count maybe twice something potentially interesting happened. I would come to a stop at a corner for instance and as I began pulling away it seemed like the accelerator cut out very briefly, almost like my foot slipped off the pedal. I could be imagining things but this came very random and happened a couple times. I also noticed the car would start in clear flood mode with my foot all the way down (at the gas station of course). I was under the impression the engine shouldn't start while doing this. These two situations led me to believe there may be something afoul with the ETC and maybe that was causing limp mode, of course this was before I took it to the mechanic. Just for shits and giggles I took off the air duct between the filter box and throttle and it had a moderate amount of oil pooled in it, there was also some in the throttle. There were black deposits in the walls of the throttle body where the plate rests but not necessarily on the plate itself. I shined a flashlight into the MAF sensor but I couldn't really tell if it was dirty with the weak light and it being midday.

Sorry about the long drawn out post, this is just really upsetting news for me.

On the little paper the shop gave me before I rolled my broke down car home it says theres a P0658 – Actuator Supply Voltage – Circuit Low

Is there a possibility I can check for opens or shorts anywhere that doesn't involve dropping the pan or would that just be a waste of time?

At transmission harness connector is a good test point however the transmissions after 2006 started having a fully integrated valvebody (ie tcm, pressure control solenoid, tcc solenoid, shift solenoids, pressure switch assembly, trans temp switch, all in an assembly which that assembly runs anywhere from 500 to 1800 depending on transmission and make model it was in. That assembly is the (transmission control module assembly) and it has to be programmed so what they quoted is not bad.

I went out and checked the transmission fluid dipstick earlier. It was light brown but clear (not opaque). It was at the full mark and didn't smell burnt or anything. Before when it temporarily went into limp mode I would park and check the transmission fluid. It used to be light pink yet clear. I always thought ATF was red but I've heard some people call fresh ATF pink. Like how someone might say mint is a shade of green when it looks more blue to me. I didn't think much of it and continued driving like that.

Is it possible coolant was mixing with the fluid? Would it be worth it pulling the plastic shroud off the front and looking inside the radiator to see if ATF is in the radiator (orange coolant). If so what shade would I expect to see? It stands to reason that if there is perhaps mechanical damage in the transmission, replacing the TCM/electrical fault would be a waste of money in a situation like this.

I also noticed something else earlier. When I was looking at the TCM connector I noticed all the wires going into it but there was this one lone red possibly orange or brown wire on the opposite side that looked like it was going into it as well. I thought that was kind of interesting, I couldn't find the end of it hanging anywhere so I figured maybe it was just the way it was made.

If I had to describe the fluid when I first got the vehicle I'd say it looked like "light pink fluid" from the second image then it turned to "good" from the first image, but still clear.

EDIT: I was looking at this (the first one that isn't blurred out) portal-diagnostov.com/en/2020/04/16/tran...tem-wiring-diagrams/

This diagram says "hot at all times" and "battery positive voltage" for the TCM fuse. At most I got it to read 30mv by probing the fuse. In both "on" and running positions.
For the trans fuse it says hot with IGN relay energized. I assume that meant when the ignition is either on or the engine is running. I tried both conditions and checked the trans fuse only to find 25-30mv at most. Both fuses are good. Does this mean anything or is it just the PCM/TCM shutting down these circuits as part of the limp mode?

I don't think it would cause the fluid to change to brown. Usually when trans fluid turns dark it's from material wear and high temps.

With the voltage being that low I would start chasing that wire upstream to see if it is higher at the source of where it's coming from. Also pull fuse to see if the power side of fuse terminal reads batt voltage if it does then plug fuse back in and disconnect trans connector and re check voltage key on if it reads batt voltage the short is inside trans. So you will then need to check the individual solinoid pins to the ground pin with multi meter and see if you get continuity. Odds are it's the tcm module assembly assuming it's a 6t series trans with the plastic front cover.

I rechecked the fuses. I did it wrong last time, looks like I might have measured voltage drop. I rechecked with the black lead on a nearby ground and had battery voltage at both fuses on either side of the fuse.

TCM connector is a bit hard to get to so in the meantime I took a sample from the radiator (it was full) and another fresh sample from the bottle of orange dexcool I put in it a year or so ago.
The sample from the radiator had a slight pink/red hue to it compared to the stuff from the bottle that was still fully orange. When I swirled the rad fluid around it seemed a bit more viscous. The premixed dexcool from the bottle just feels thinner between my fingers. The radiator sample feels thicker, slicker and left a sticky feeling. It also had a fishy/musty/burnt smell to it. Is this an indication of ATF/Coolant mixing? I just want to make sure there isn't an underlying problem that will destroy the trans after it gets fixed.