4L80E problems

[hunter4ever12]

So if you frequent here, you probably remember my post a while back about having a lack of torque/low end power. Well I may have narrowed it down a bit but now have another issue.

I hooked my 94 K2500 up to my buddies high dollar Matco scan tool and found a code stores that said torque converter clutch stuck off. I have a scan tool myself but not as in depth as his Matco one. My scan tool never picked up this code and I also have not had a check engine light come on since clearing all codes my scan tool did pick up. But anyways his tool found it. So I thought ok most common cause of that is tcc solenoid. So I went ahead and dropped the pan and replaced that as well as both A and B shift solenoids while I was in there. Now it needs noted, that beforehand I had no driveability issues other than my lack of low end torque. After replacing the 3 solenoids reinstalling the pan and filling it back up with ATF. I test drove it, this is where the problem began. Now I have no overdrive it shifts 1-3 smooth and with no problems and the torque converter will even go into lockup in third gear(from what I understand the 4L80E has 4 gears but it has 1st, 2nd, 3rd, 3rd lockup, 4th, and 4th lockup. I tested and varified 3rd lockup was working with one foot on the gas and tapping the brake with the other and my RPMs jump up showing me it's coming out of 3rd lockup) but it will not shift up into 4th at all. Now I don't really understand how installation of new parts could make a problem worse.

I went ahead and got a new torque converter for it as well just in case the solenoid didn't fix my issue (which it didn't) but I just wanted to see what everyone else's thoughts were before I pull the transmission and put a new converter in it. Although I will say I'm fairly certain I do have an issue with the converter. If the solenoid didn't fix my problem that leads me to believe the problem lies within the torque converter clutches themselves, that, and after installing the solenoids and putting brand new fluid in it and driving it maybe 20 miles the brand new fluid already smells burnt and isn't bright red as you would expect it to be. It doesn't look full on burnt but it does have a brown tint to it.

Any help as always is appreciated

[j cAT]

If it shifts good 1-3 but 4th don't , then the torque converter is not the problem..

could be and most likely the shift valves that you messed with.

[hunter4ever12]

Ok I guess I miss worded my post, I know not shifting into 4th is not the torque converter, as far as replacing the torque converter goes I am only doing that because I'm still getting a torque converter clutch stuck off code even after replacing the solenoid. As far as not shifting into 4th I don't really understand how replacing my old solenoids with completely brand new ones would make things worse. I mean stranger things have happened but in my experience it's extremely rare to find a part "bad" from the box.

Any ideas on how to troubleshoot why it's not shifting into 4th? That's more of what I was getting at. I tried to find a procedure list online but all I can find is everyone saying to replace the solenoids (already did, and had 4th with old solenoids, now have no 4th) normally I would go through the trouble of reinstalling the old ones for a baseline, but I already tossed the old ones and they are long gone.

[j cAT]

the solenoids must have the proper resistance. these did/do change depending on the model year . so did you measure
the old compare with new?

then the connections to these and also the tranny connector external .

the solenoids are the electrical the fluid side/valve maybe sticking.

normally when this type stuff happens the tranny shop will do the pressure/shift test. then they can tell what's not working properly.

you never did post the tranny GM drivetrain code .........

my guess is , but with no codes a big guess the sun shell has a crack...

if you had dexron III in it perhaps a very good guess..

[Schurkey]

Originally Posted by hunter4ever12

I hooked my 94 K2500 up to my buddies high dollar Matco scan tool and found a code stores that said torque converter clutch stuck off. I have a scan tool myself but not as in depth as his Matco one. My scan tool never picked up this code

Drop-kick your "scan tool" into the trash can. It's worse than not having one at all. If a scan tool can't read transmission, air bag, ABS, etc, it's worse than worthless since it's giving you a false sense that there are no codes stored.

Is your "scan tool" an actual scan tool, or is it some consumer-crap "code reader"? A "code reader" is not a scan tool.

Originally Posted by hunter4ever12

So I went ahead and dropped the pan... ...reinstalling the pan and filling it back up with ATF.

How many quarts did it take?

Originally Posted by hunter4ever12

that leads me to believe the problem lies within the torque converter clutches themselves

The torque converter clutch (TCC) works now...right? So the converter clutch is probably JUST FINE. The poor low-speed power may have been a failed sprag in the torque converter, not the clutch.

Well, OK, the sprag is a one-way clutch, but that's nothing like the TCC. You'll want to be clear about WHAT in the converter may have failed, or you're going to confuse people.

Originally Posted by hunter4ever12

after installing the solenoids and putting brand new fluid in it and driving it maybe 20 miles the brand new fluid already smells burnt and isn't bright red as you would expect it to be. It doesn't look full on burnt but it does have a brown tint to it.

If you didn't install 12 quarts of fluid--or more, along with a trans cooler flush--the new fluid has been contaminated by all the old fluid you didn't remove. Of course it looks burnt like the old fluid--it's about 1/2 new, 1/2 old.

Originally Posted by hunter4ever12

it's extremely rare to find a part "bad" from the box.

Not like you'd expect or hope for. The Communist Chinese can screw-up ANYTHING; and sometimes even domestic product isn't QA'd like it should be.

Originally Posted by hunter4ever12

Any ideas on how to troubleshoot why it's not shifting into 4th? That's more of what I was getting at. I tried to find a procedure list online

Time to buy a REAL service manual for that truck.

[hunter4ever12]

So I do actually have a "real" scan tool... I recently moved and alot of my stuff was still in storage in a town about 45 min away (I moved to a very rural area) I went and got my scan tool today and hooked it up for furthermore diagnosis. I deleted all codes to begin with, and then ran the vehicle with it still hooked up, the only code that came back was code 82 shift circuit solenoid 1-2 fault. The tcc code did not come back...When looking at live data I found that the 1-2 shift solenoid is "on" with the vehicle in park idling, that doesn't sound right to me, I would think it should be off correct? Also I also found that according to the scan tool my trans oil temp is -40 deg, which I know is not right so looks like I need a trans fluid temp sensor ( that could be causing my lockup issues, and very likely is) I also found that my throttle position sensor voltage reads at 5.8 not sure that's right either, it does change with the throttle being pressed buy that still seems wrong, and furthermore my TPS sensor reading at an idle is at 54% and doesn't change when the throttle is pressed or not...So with that being said either I have 2 failed sensors, or something wrong with the ECM. This evening I'm going to try unhooking my TPS and driving it to see if I get overdrive back because from what info I have gathered by unhooking the TPS the ECM reverts to a set shifting mode. I'm not so sure why would a circuit fault with my 1-2 solenoid cause me to loose overdrive? I know the 1-2 solenoid does control the 4th gear shift but with the other issues I have found I want to rule them out first. From what I've gathered from my service manual as far as the code 82 goes, it could be a problem with the ECM, or it could be the voltage on the solenoid is either high or low for at least 2 seconds... So with that being said what's next after I perform the tests I already mentioned above. What test procedure (s) can be performed to further narrow this down?

[Schurkey]

Originally Posted by hunter4ever12

I also found that my throttle position sensor voltage reads at 5.8 not sure that's right either, it does change with the throttle being pressed buy that still seems wrong, and furthermore my TPS sensor reading at an idle is at 54% and doesn't change when the throttle is pressed or not...So with that being said either I have 2 failed sensors,

Huh? Throttle position sensor IS the TPS sensor. Either it changes as you apply throttle, or it doesn't. You do not have two different TPS sensors.

Originally Posted by Schurkey

Time to buy a REAL service manual for that truck.

[hunter4ever12]

Not trying to be an asshole... But I'm not stupid can we make that clear?

Ok now that that's clear...I know the throttle position sensor and the TPS are the same.... So if you would read the post a little closer, you would see what I said is my TPS had a voltage rating of 5.8 volts at idle and I confirmed it did change when the peddle was pressed down(let me make that as clear as possible... the voltage reading on the scan tool for the TPS did fluctuate/change depending on throttle position) I also said my scan tool read that the TPS showed 54% at idle(it should be 0%) so that's a problem (let me make this clear as well this is a completely different reading and line on the scan tool, yes it's reading the TPS just as the above reading was...But they are two separate "lines" or "categories" on the tool)... Furthermore when pressing the peddle down the percentage does not change, it stays at 54%(it should go up in percentage the more the throttle is pressed towards WOT, and at wide open it should read 100%

So with that being said, once again, not trying be be that guy but.... If your post is only to criticize me and not something that's actually helpful, what's the point of it?

[Schurkey]

Originally Posted by hunter4ever12

I know the throttle position sensor and the TPS are the same.... So if you would read the post a little closer, you would see what I said is my TPS had a voltage rating of 5.8 volts at idle and I confirmed it did change when the peddle was pressed down(let me make that as clear as possible... the voltage reading on the scan tool for the TPS did fluctuate/change depending on throttle position) I also said my scan tool read that the TPS showed 54% at idle(it should be 0%) so that's a problem (let me make this clear as well this is a completely different reading and line on the scan tool, yes it's reading the TPS just as the above reading was...But they are two separate "lines" or "categories" on the tool)... Furthermore when pressing the peddle down the percentage does not change, it stays at 54%(it should go up in percentage the more the throttle is pressed towards WOT, and at wide open it should read 100%

TPS voltage at idle should be MUCH lower than 5.8 volts.

If the TPS voltage is changing as the throttle opens, but the TPS percentage doesn't change, I think that either the scan tool or the on-board computer is faulty. My bet is the scan tool, but I've been wrong before.

Connect the scan tool to another "known-good" vehicle and see if the TPS readings are out-of-spec on that one, too.

[hunter4ever12]

I'll try that tomorrow, or try another scan tool and see what results I get from it. I actually have access to several different ones (through co worker friends, and I have my 2 as well) i work at a feedlot and farm shop as a mechanic, but about 98% of what I work on on a daily basis, are either obd2 Powerstroke diesels, semi trucks, or heavy equipment/farm equipment. So my obd1 gasoline engine skills aren't what they could be compared to other vehicles. As far as I'm concerned obd1 is a pain in the ass.

But anyways I'll keep digging on this issue and see what happens and report back. But just to clarify, what your saying is; the readings the TPS showed on the scan tool CAN NOT be from a faulty TPS correct? It's either an ECM or scan tool problem. That's how I interpret what your above post says.

[Schurkey]

Originally Posted by hunter4ever12

I'll try that tomorrow, or try another scan tool and see what results I get from it. I actually have access to several different ones (through co worker friends, and I have my 2 as well) i work at a feedlot and farm shop as a mechanic, but about 98% of what I work on on a daily basis, are either obd2 Powerstroke diesels, semi trucks, or heavy equipment/farm equipment. So my obd1 gasoline engine skills aren't what they could be compared to other vehicles. As far as I'm concerned obd1 is a pain in the ass.

But anyways I'll keep digging on this issue and see what happens and report back. But just to clarify, what your saying is; the readings the TPS showed on the scan tool CAN NOT be from a faulty TPS correct? It's either an ECM or scan tool problem. That's how I interpret what your above post says.

I don't guarantee anything that doesn't happen on MY scan tool.

I do not understand how the same data stream that shows change on TPS voltage with application of throttle, does not show change on TPS percentage. To me, that has to be a scan-tool problem.

But then, 5.8 volts at idle for TPS voltage is crazy, too. It should be less than one volt unless GM changed their system.

That's why I suggest re-checking with another scan tool, or verifying that your scan tool shows proper readings on a different vehicle.

[hunter4ever12]

Originally Posted by Schurkey

I don't guarantee anything that doesn't happen on MY scan tool.

I do not understand how the same data stream that shows change on TPS voltage with application of throttle, does not show change on TPS percentage. To me, that has to be a scan-tool problem.

But then, 5.8 volts at idle for TPS voltage is crazy, too. It should be less than one volt unless GM changed their system.

That's why I suggest re-checking with another scan tool, or verifying that your scan tool shows proper readings on a different vehicle.

Gotcha that makes sense...One other question I do have though (because as I said I'm not as familiar with this vehicle as I should be) is; from what I've read, I believe my pickup has a TCM (transmission control module) that is completely separate from the ECM is that correct? And if yes I'm assuming the TCM feeds the ECM data and Ultimately the ECM controls the TCM right?

So if the above is all correct, I could very well have another factor to throw into to the equation, and that factor is the PCM.

I will say this, upon further diagnosis last night I still do not have 4th at all, but I also noticed my kickdown function was not working either. So here is how I noticed that. I'm driving along at roughly 35-40 mph. I push the peddle to WOT, and it doesn't downshift. It stayed in the current gear and did accelerate, but very slowly and sluggish compared to if it would have down shifted.

Now from what I've gathered on my vehicle (because it's a 94) the kickdown function is controlled through the ECM and there is no actual kickdown cable that could be manually adjusted, I'm about 99% sure that info is correct because I do not have a kickdown cable going to my TBI. So if this is correct, the way I look at that is it's another sign pointing to a bad ECM or possibly TCM, would you agree?

[Schurkey]

Originally Posted by hunter4ever12

Gotcha that makes sense...One other question I do have though (because as I said I'm not as familiar with this vehicle as I should be) is; from what I've read, I believe my pickup has a TCM (transmission control module) that is completely separate from the ECM is that correct? And if yes I'm assuming the TCM feeds the ECM data and Ultimately the ECM controls the TCM right?

So if the above is all correct, I could very well have another factor to throw into to the equation, and that factor is the PCM.

I will say this, upon further diagnosis last night I still do not have 4th at all, but I also noticed my kickdown function was not working either. So here is how I noticed that. I'm driving along at roughly 35-40 mph. I push the peddle to WOT, and it doesn't downshift. It stayed in the current gear and did accelerate, but very slowly and sluggish compared to if it would have down shifted.

Now from what I've gathered on my vehicle (because it's a 94) the kickdown function is controlled through the ECM and there is no actual kickdown cable that could be manually adjusted, I'm about 99% sure that info is correct because I do not have a kickdown cable going to my TBI. So if this is correct, the way I look at that is it's another sign pointing to a bad ECM or possibly TCM, would you agree?

Originally Posted by Schurkey

Time to buy a REAL service manual for that truck.

The 4L80E is electronically controlled, but I don't know if it's a stand-alone module or integrated into the same computer that regulates the engine.

Wild Guess: Integrated into the engine computer.

[Blue Bowtie]

Be aware that the early solenoids had a different resistance range than later models. I don't recall the exact numbers or years, but there ARE differences and the solenoids are not universal. I know that after the 2000 model year they standardized, but there were differences in 1993-94, some 1993-up variants, and 2000-later types.

Verify that the original solenoids are the same resistance as their replacements.

[maxwedge]

No stand alone trans control module, all part of the pcm.