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Transmission Fluid flush and/or sensor replacement?

8K views 19 replies 10 participants last post by  sbr711 
#1 ·
I own a 2013 Hyundai Sonata. Two months ago I realized that my transmission shift occasionally while I am driving, especially when the weather is cold and I park my vehicle for more than one day. Then my engine check light came, after two days it went off. I went to the dealership and ask for a multi-point inspection (without telling the inspector the transmission problem), they recommend a transmission fluid flush, then I went to an auto part shop to ask for reading engine check light code, they see P0711. After researches online, I understand this code is about transmission fluid or transmission fluid sensor defect.
My question is that, would a dirty transmission fluid cause the P0711 code, as some people stated online ?
Would the transmission sensor change require fluid flush ? Should do one or both ?
I want to have some more information before going to the dealership because my car is not under warranty anymore and I would have to pay out of pocket, the dealer quote $230 for fluid flush and I see online the sensor change would go up to $700.
Currently the car is working normally.
Please help understand the situation more.

Thanks
 
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#2 ·
Personally I would check the fluid level, erase the code and see if it returns. If you're due for a flush, it should probably be done anyway. Do a search, there may be a TSB on your car. I did a prelim search and there's a few that relate to the transaxle.
 
#4 ·
Hi dougmcp,
Thanks for the quick reply. I am thinking to do the flush first and then wait and see if the problem will come again. But in case the problem persist and I have to change the sensor later, wouldn't that be a lost for the flush I have done, I am not sure while changing the sensor they would have to empty the transmission fluid (sorry if that sound stupid but I am really ignorant about cars).
I have done some search about TSB and going through.
thanks
 
#5 ·
How many miles are on your car? Personally,I would stay away from a flush. If you have a lot of miles on the car,a flush can dislodge particles/crud which can block passages of the intricate valve body. Best to do a drain and fill imo.
 
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#6 ·
That fluid temp sensor is a common failure part, and I think it requires replacing the harness as well. The old fluid will drain out when the parts are replaced, so it'll all be done at the same time.
 
#9 ·
@Airforce1, thank you! My car is at 68K miles, I've never refill the transmission fluid and I've read about your concern also elsewhere online. I think I will be strongly considering a refill instead of flushing.
@80schild, you touch my main concern, I don't want to refill two times.
Thanks everybody for the help.
The OEM (in the Kia service manual) method/procedure is a single simple drain and fill, so just do that. Never use a "Flush Machine". Don't ask why but you can guess!
 
#12 ·
If a flush "causes" a transmission to fail, then it was getting ready to fail anyways. Still, a simple drain and fill is all that's usually ever needed.
 
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#14 ·
In my case, I don't think so. The transmission only had 36K miles on it and was shifting fine. From my research, the power flush (not the same thing as a simple drain/fill) likely loosened some clutch-pack/grit that then got into the very fine solenoid passages and plugged them up which caused major slippage of my bands and then requiring a rebuild. This is a VERY common issue with these "Power Flush" procedure and the transmission shops will NOT warranty their flush against causing issues. YMMV.
 
#13 ·
Eh. for what it's worth i'm around 65k and the trans doesn't want to shift when really cold. I've heard from many others that the trans fluid the car came with was junk and with a flush or drain and fill they will use the new full synthetic SP4-M.

The Original was SP-IV, SK ATF as shown here
http://www.hyundaisonatamanual.com/sonata-296-recommended_lubricants_and_capacities.html

I will be getting a flush done at the dealership near my work, they said they would do it for $130 to beat the other price quotes I recieved, so I really can't pass it up.

Look at it this way, our trans takes 7.5 quarts and with a drain and fill you usually get about 4-5 quarts out and the same amount in. That means your old burnt/used fluid will mix with your new fluid. If you fill with a different spec fluid than what was originally put in the car (SP4-M) you basically have half and half.

I figure I will get the flush then a couple months later refill with Amsoil ATF.

AMSOIL Signature Series Fuel-Efficient Synthetic Automatic Transmission Fluid

BTW the car is fine now that it's not extremely cold outside.
 
#15 ·
FYI guys, just got the trans flush done at the dealership by my work. Drain and fill is always less than 5 quarts (4-5 quarts), and (are you ready for this?) transmission flush replaces 12 quarts....

I'm pretty happy I got the flush instead of doing the drain and fill by myself, though knowing this I might not go through with the Amsoil trans fluid since I would be replacing less than half of the total fluid.

Next on the list is pcv delete and exhaust install!
 
#16 ·
FYI guys, just got the trans flush done at the dealership by my work. Drain and fill is always less than 5 quarts (4-5 quarts), and (are you ready for this?) transmission flush replaces 12 quarts....

I'm pretty happy I got the flush instead of doing the drain and fill by myself, though knowing this I might not go through with the Amsoil trans fluid since I would be replacing less than half of the total fluid.

Next on the list is pcv delete and exhaust install!
Twelve quarts??? Sounds excessive to me by about 4 quarts. Can someone confirm that? Not doubting you,I am doubting what the dealer told you.
 
#17 ·
The transmission flush machines use 3-4 gallons of new ATF for the fluid exchange. Can you verify that they used a flush machine?

Another method would be to drain/refill ATF and drive 5 minutes, and then repeat as needed(3x-4x) which would be the 12-16 quarts.
 
#19 ·
It's because the machine will use a gross amount of ATF, the 12 quarts listed, since old and new ATF are mixing in the pan, in the torque convertor, in the valve body, and at the ATF cooler. Capacity and flush machine amount don't relate 1:1 ever.
 
#20 ·
0711/12/13 to original owner will get you a new A/T internal harness-temp sensor replacement and 5qt SP4-M if 2.4L,, and 6qt SP4-M if 2.0 Turbo via Powertrain warranty

2nd and later owner only get 5yr/60,000 coverage

Flush is waste of expensive ATF.. first part come out dirty, then progressive clearer as new oil used to chase old oil out mixes and comes out.. Look at it as flushing $50-75 down the drain..
 
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