99 Chevy suburban transmission shifting problem

C

Christine4

New member
Joined
Sep 21, 2014
Messages
7
Reaction score
0
Points
0
I have a 1999 Chevy suburban 7.4L it has 187,000miles.
It has intermittent shifting problems some days it runs fine most days shifts really hard in 1,2,3 but at highway speeds it is fine. It throws a dtc p0712 transmission temperature sensor.I took it to a transmission shop they replaced the internal harness. Got it back and it did the same thing and threw the same code. Took it back he said the transfer case seal needed fixed. So he replaced the seal. Got it back and it did the same thing and throws the same code. So I took it back and he said there is a short in the vcm/pcm and it needs replaced. I ordered it and put it in myself. After all this it is still throwing the same code and shifting hard intermittently. Same problem I've spent close to $1000
Someone help please!!!
 
The first thing listed for this code is the sensor itself and you make no mention as to whether it was replaced. All other remedies point to the wire harness or poor connection. Is this shop a state licensed shop with ASE certified mechanics? Have you pursued filing a complaint against them? Have you tried another shop?
 
You read these stories time and again. Shops replace parts and don't fix the problem and people still pay them. It doesn't make sense.
You are already 2/3 of the way to a completely rebuilt transmission. Did you ever replace the sensor? Transmissions are complicated. It's hard to armchair problems with them. I have intermittent issues on mine also, but rather than putting money into a guessing game, I'm waiting to replace it. It has 175K miles and that is usually the end of reliable life on them. I have the 4L60E, you probably have the stronger 4L80E.
 
Wire harness and sensor was replaced the first time I took it in. One thing I forgot to mention that I have noticed is in the morning when I go to work and it's cold outside it runs fine. After work on my way home when it's hot outside is when it shifts hard.
 
did the shop use a scan tool to check what the transmission fluid temperature reading is when the code is thrown?
 
well you have to establish whether the transmission is really exceeding the temperature that throws the code which would mean there is something wrong that causes excessive temperature or is it a false code. Does the vehicle have a separate trani cooler or is it part of the radiator? Is the engine running higher temperatures than normal?
 
Laniohan4 said:
He didn't say what the temp was when it threw the code.
Click to expand...
Judging by the effectiveness of his work so far, he probably doesn't know how to read it. It takes more skill to challenge the "why" and not just the "what".
 
So what's happening is when the code is cleared the temp on the scanner is reading 150 degrees. when the code is thrown it's showing 350 degrees. But the vehicle hasn't even ran for very long? It seems like everything that could be the problem has been replaced?? When the code is cleared I have only driven down the block before it throws the code. I don't have a separate transmission cooler.
 
well the temperature isnt supposed to be 350 so it is throwing a valid code. Is your transmission cooler clogged?
 
That's a good possibility and why a mechanic should validate and over-temp condition instead of just assuming the sensor is bad. Meantime you are out about a grand and just now getting to the problem. I'd have a serious talk with this mechanic. I hate to sound chauvinistic, but with a nickname of 'Christine4' I assume you are female. This guy seems to be taking advantage of you.
 
Dont forget Christine was the name of a possessed car in a Stephen King novel
 
At this point I hope it's just the line, but wouldn't I be able to smell it?? The fluid looks and smells fine.
Great movie!! Never read the book.
I don't think she possessed I've had her for seven years and we've been through a lot together. This is the first big issue I've had.
 
you have fresh fluid and it might take time for it to start breaking down. How is the engine temperature, normal?
 
Engine temp is normal. When I took it in the first time the fluid looked good and no smell. That's when the harness was replaced and that's when I got new fluid, filter. This was about six weeks ago.
 
If the trans temp is consistently climbing to 350, it's going to continue to throw a warning. That's the purpose of the sensor. When you get a warning, you don't change the warning system, you validate the symptoms first. i.e. check the temp. Same as you would if the coolant temp ran hot. Smells and fluid discoloration are signs, but may not occur right away.

A good system flush might be in order if you have a blockage. Dexron VI is the latest and best fluid grade today. It's pricey so i wouldn't add it until you know you have it fixed and won't be draining it again.

http://www.gmls4.com/index.php?topic=604.0
 
Quick update
Hope nobody has to go through this problem but just in case,
I took my suburban into a different shop told them the long story and dropped her off. A few hours later they call and say good news!! It is a short to ground on the harness coming out of the transmission. Which I assumed was checked because I was told the wires were traced to a short in the vcm. Anyways I hope this helps and possibly saves some one some money , since I spent around $1000.00. LESSON LEARNED!!!
Thank you for the responding posts
 
sorry you had such an expensive lesson and that the quality of shops varies so much
 
You must log in or register to reply here.

Share this page

Back
Top