Thanks Beater for the update, it's great to get feedback! I'M sure you and Derk are right about the TCM or TCU being separate, GM combined the two controllers for many years, (the PMC and TCM or TCU) but with Saturn pretty much doing there own thing, I would not be surprised...good to know, considering the cost for replacing the combined controllers. I do see a lot of manufacturers putting more and more software inside the PCMs, so it stands to reason connecting more and more external modules together with bussed date to free up some room inside the PCMs. Good call, Derf, you are right on target! And, just an FYI, most trans shops recommend NOT changing the trans fluid on anything with over 100K miles, if it has never been touched. It usually causes more problems than it fixes. Trans fluid is high detergent, so it cleans, lubricates and provides hydraulic operation. Sometimes the new slick fluid will cause slipping problems in high mileage units that was not evident with the old degraded fluid. I recommend about every 60K miles, some shops recommend 30K for warranty coverage on rebuilt units. Anyway, thanks Beater, check back soon and let us know how that Ion is doing!

 

210 miles logged and no P2138 code thrown. I think it's time to celebrate now. Woohoo! Stupid gas station mechanic wiring hack job......GONE! lol

Now the tranny has calmed down quite a bit, but it has acted up once since making my repairs. Could this still possibly be just a dirty trans oil issue causing the trans to overheat? I only changed what was in the pan so there was still 6-7 quarts of really bad fluid in the torque converter. Since it has had time to circulate, would doing another drain be viable?

 

Alpha ?

 

Ya I know he said not to change the oil, but it was doing this before I changed the oil and seems to be doing it less after I changed the oil. Just taking a shot in the dark here before really digging into this. I can do just about anything outside of the trans and engine. But when it comes to internals, I know just a little.

 

Hello Beater, to answer your question: I wouldn't touch it, seriously. I believe that wiring issue with your APPS was causing the majority of your trans problems. If it has only acted up once since the wiring repairs, I would still see if there are any codes stored in the trans controller (TCU) before doing anything else to the trans. You will need a scanner, not a code reader. Some trans shops like Certified Transmission will scan your vehicle for free, call around and see who can pull trans codes, and see what they charge. Some shops will do that for free, just to get you in the door. Make sure you tell them "Trans scanned for codes, not a code reader." I think that would be the next logical step.

A 4T45E life cycle is about 100 to 150,000 miles, give or take depending on abuse and maintenance. If that trans has never been touched, count your blessings, and save your money, you may be at the beginning of the end for that trans. As far as the fluid, don't take my word for it, call a few shops in town, tell them you have a trans with 150,000 miles, and want the trans flushed...see what they say. I would recommend having that trans scanned for codes before doing anything else, that may tell you everything you need to know, especially if there's an P-1811 or equivalent...slip code stored in memory. But, if you had the codes cleared after your APPS wiring repair, the TCU may have to see the fault 3 times to set a code, either way, I would still have it scanned. If there are no codes, drive it until it acts up 3 or 4 more times, and have it scanned again. If the trans went into fail-safe, it set a code in the TCU, either in the "Current Codes" or "History Code" TCU memory. If you do find a code, get back to us and we'll go from there, before having anyone touch it. A second opinion never hurts.

 

Derk's happy you're here....

 

Who, me? Happy to be here Derfie Derk...LOL! Sometimes I type too fast, no spell check on names, LOL! You Guys and Gals are the best!

 

Alright, thanks. That's good to hear I can possibly get it scanned for free. I will wait till it acts up a few times(if any) and go get it scanned.

 

Update: Good news, 600 miles and no error code. Woohoo! Semi good news, it still does the tranny hard shift, but I've got it pinned down to exactly when it does it. Ya ya, I know to just scan it, but no fun in that! I've learned the normal engine temp on my gauge in the dash. When the engine goes slightly above that temp, it starts to shift hard. Seems like it does this before the fan turns on and the thermostat opens more to cool the engine. So does this in fact sound like the Engine Temp Sensor?

 

Hey Beater, that is good news! Knowing exactly when the trans acts-up is a great start in diagnosing the problem. But, to answer your question, it's hard to say for sure without looking at the temp sensor data. Without knowing what the exact temp is you're talking about, how long it takes to reach that temp, or knowing when your Saturn goes into closed loop, there's just not enough information to work with as far as a temp sensor being the problem.

What I can tell you is it should not take more that 10 to 15 mins for the engine to reach operating temp (closed-loop) with outside temps in the 60's or 70's. Until the engine reaches operating temp, the PCM is in open-loop. Meaning the controllers aren't looking at all the sensors data, like oxygen sensors to control fuel trims (fuel metering) or cell-taps to control shifting, so the PCM and TCU control the engine management and transmission operating functions off basic parameter settings programmed inside the control units. Live data they look at when cold (open loop) is engine temp, intake air temp, engine rpm, vehicle speed, cam and crankshaft sensors (on most vehicles). But like I have said before, if it starts shifting okay after you turn the engine off, then back on again, it sounds to me like the TCU is seeing a problem, perhaps only after the vehicle goes into closed loop, or reaches a certain temp then the TCU is boosting line pressure trying to compensate for the problem or malfunction.

Ya ya I know too, but I'm still not sure why you are unable or unwilling to have the TCU scanned for codes? No hard feelings, but without that information, it's anyone's best guess. You can try a temp. sensor, they do go bad, and cause all kinds of issues, but I seriously doubt that is your problem. The PCM may command the TCU to delay the shifts a little in order to reach operating temp, but not after. If the trans shifts fine when cold, then shifts hard when warmed up, that sounds like a slip problem, sensor or solenoid malfunction to me. Now we know the only time it slips or malfunctions is when it's hot, like perhaps an input speed sensor with high resistance when hot...but that doesn't mean the temp sensor is problem, unless of course, the engine and /or trans are overheating.

Exactly what temp are the fans coming on? To know for sure, I would check that gauge with a scanner to see exactly what the temp sensor is reading when the fans are commanded on, and check the block and head temps with a laser temperature gun to see if the temp sensor is accurate, if you think it's a temp problem, that's the best, most accurate way to know for sure. Dash gauges are not as accurate as a scanner in most cases.

I would still scan the TCU for codes (with a scanner not a code reader) before trying to diagnose everything else under the hood first. Why take a 20 mile trip, when you could get there in 5, what's the fun in that? For us Mechanics, time is money, if the trans is acting up, that's where we start...then backtrack from there, not the other way around. I understand your logic around the temp concern, and obviously there is a correlation, but I believe that is the condition under which the problem exists, not the cause of the exact problem.

Just to clarify, here is an example of cause and condition. A few weeks ago a new customer came into the shop and said he wanted his B1S2 Oxygen Sensor replaced. When I ask him why, he said O' Reilly checked it with a code reader and they said it had a bad Oxygen Sensor. He didn't know what the exact code was, so I scanned it. Sure enough, lean code, Bank 1, Sensor 2. I explained that the O2 sensor was probably alright, and was doing it's job, letting us know that there was an engine problem. Come to find out, he had a vacuum hose that was leaking at the intake manifold. I could have replaced the sensor, but the problem would have still been there. The condition was a check engine light, with an O2 code, no power on acceleration or under load, and sometimes idle was too high...but the cause was a vacuum leak, not the O2 sensor it's self.

In your case, the temp is the condition under which the problem exists, not necessarily the cause of the malfunction. Heat is a major factor in electrical components, if they have a problem (worn or sticking mechanically) heat can increase internal electrical resistance, causing the circuit to draw too many amps. Heat is also a factor in clutch and band applications, as the trans temp increases, the fluid thins out, new or old fluid, makes no difference, but new fluid is slicker, which will cause more slippage in a trans with high mileage. Also, the trans will not adapt, or monitor cell-taps for shift quality until the engine goes into closed loop, again, cause and condition. The TCU and/or PCM is seeing a problem and trying to adapt, or compensate, but that doesn't mean the controllers are at fault, they are doing what they are programmed to do. Boost line pressure if they see any slippage, or fail-safe to second gear in the event of a major failure.