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Elantra Gls 05 - High Engine Rpm Issue

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7.2K views 3 replies 2 participants last post by  PLP  
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#1 ·
Hello,

I have an 05 Elantra GLS auto transmission, ~83000 miles. Last Friday, the car was driving fine. I didnt drive it on Saturday, but when I started it up Sunday night, that's where the issue began. First, when I shift into reverse, the car makes a noise like as when you go over a pot hole. Idle RPM is around 800.

When I press the gas pedal, usually the response from the car to go forward is almost instantaneous, but now it take a second or two from the time I press down the gas pedal to when the car moves forward. The process is smooth though, no hicups as it does that. Next, when I was driving on the highway between 70 - 80 MPH, the car's RPM was 4000 - 4500. It even sounds like the engine is "working harder" than it usually does. The 'Check Engine' light is also on with these codes: P0700 and P0885.

Another thing I noticed is that the car alternates between running fine and running with the conditions described above. If the car run with the symptoms described above, I shut off the car and restart it. Then it will run fine, but the check engine light will stay on. Then if I turn off the car and restart it, it will go back to the mode where I have the issues.

From some research, the P0700 code just means that the TCM has the actual code which is P0885. According to the tech manuals at www.hmaservice.com, the P0885 has the following probable causes.
- Malfunction of the A/T control relay
- Malfunction of connector
- Malfunction of the PCM

The car actually ran fine today, with out any issues but the Check Engine light is stuck on.

Does anyone know how to replace/service this PCM item? Or maybe this issue is covered under 100,000mile warranty?

Any help would be greatly appreciated.

Thank you.
 
#3 ·
all right, I looked it up and here is what I found.

Manual (5 speed) in 5th gear will be going about 114 km/h at 3000 RPM, while at 3500 RPM it will be at about 133 km/h (71 MPH and 82.5 MPH respectively).

However, A/T has different gears (much longer) and the final ratio is different as well.
Hence, it will be 130 km/h @3000 and 151 km/h @3500 (81 and 94 MPH).

If you hit 3500 at 80 MPH then something is wrong. Initially I would suspect torque converter to no lock.

How to check it? When the torque converter is locked up slight changes in gas will not affect RPM, meaning it will act as it was manual transmission. The gear is "locked" with engine.
Hence, while going 55 MPH you should be at about 2000 RPM. After engine has reached its operating temperature the torque converter should lock up in 4th gear.
So, keep going steady at 55 MPH and gently push the gas - would RPM increase radically? If so, but the speed remained almost same, torque lock is not on.
If the RPM increased a little bit along with the speed - either you did not push the gas deep enough (I would say 1/5-1/4 of travel) or most likely the torque lock is working fine.
If you push too hard - the torque lock will disconnect and RPM will start floating again (just like it is in other gears).

Furthermore, at higher speeds it should be ON regardless of your foot on the gas. Hence, at 70 MPH it should behave same - push the gas and RPM go slowly with speed.

So, run the tests and update.


Oh, the torque lock is electronically controlled, but it may fail due to low fluid level or very contaminated fluid.
 
#4 · (Edited)
this crappy edit thing here...

I forgot to add that the torque converter lock may seem to act as overdrive. It is not.
It does indeed lower RPM, but only because it "locks" the gear. When it is not locked the gear, even being engaged, will use the torque converter as it was designed, meaning the RPM can fluctuate/float. It feels like slipping clutch in manual transmission.
Overdrive, on the other hand, is the last, tallest gear. Hence, you could say the tranny has 3 gears plus OD.

If the torque was switching into different/taller ratio then it would be extra OD. Otherwise we simply are talking about locked torque converter and simply all gears you have.
 
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