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7 Series - E38 (1995 - 2001)

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  #1  
Old 03-05-2014, 11:04 PM
lv740il lv740il is offline
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p0740 code *newbie*

Hi, new to the forum. I have searched around the site for the code fix on this site. No real answer. My tranny will slip a little in first to second on a cold start, but after the car is warmed up the tranny shifts fine. I erased the code and drove the car 30 miles no light, then let the car sit and the light immediately popped back up as soon as the car was started. I hear a slight whine from the transmission on cold starts from first to second. Planning on doing a tranny drain and fill this weekend, but want to make sure that could fix it or if i need to purchase a tcc solenoid as well. The OBC shows speed sensor as well. 260k miles on the car, bought it from an auction so im not sure the history of the vehicle. No other problems with the car, interior and engine are really clean, so i am assuming the car was well taken care of. The transmission doesnt slip on the highway and goes into all gears.

Thanks for any help!
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  #2  
Old 03-07-2014, 02:16 PM
hermosan hermosan is offline
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I have the same car . Had the same code, transmission issue. only 130000 mi. Code says torque converter circuit open . Had tc changed out last week , twice, now its making vibrating churning noise at idle and accelerating. Mechanic is clueless. rebuild company said poor installation. now I have a useless car.but no cel. It is common problem but didn't expect this after $1200.
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  #3  
Old 03-07-2014, 02:26 PM
CitizenOfDreams CitizenOfDreams is offline
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Quote:
Originally Posted by hermosan View Post
Code says torque converter circuit open . Had tc changed out last week , twice
???

The diagnostics says "torque converter circuit" - meaning the electrical solenoid - and you replace the torque converter itself, which has no electrical parts whatsoever? What exactly was your reasoning?
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  #4  
Old 03-07-2014, 03:54 PM
hermosan hermosan is offline
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Reasoning.

My reasoning was based on every post and website I could find on the subject plus advice from two transmission shops. I first had the "sealed " transmission fluid and filter changed. Which helped performance but did not keep the code from re playing. The cel has not come back on so I expect that the solenoid is working . I just wonder why this noise is happening. I stood under the car with engine running while the mechanic indicated with his stethoscope and said first rebuilt tc was faulty. He then replaced it with my original tc we had re built and now has a new noise. Is he full of s$#&! I don't know. maybe he f%$#ed it up. How would I know. I know one thing, after owning this car for two years now is that I do all maintenance and repairs myself because I've noticed that others don't seem to care enough to do things right. I couldn't do this one .
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  #5  
Old 03-07-2014, 04:17 PM
lv740il lv740il is offline
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Mine only makes the noise at cold start, after the car is warmed up I hear no noise and the transmission shifts perfect. Going to replace the tcc solenoid and flush and run new fluid. I'm hoping it's just the sensor since if I erase the code it doesn't come back until I turn off the car and let it sit for a little.

Thanks for the help!

Fingers crossed that I don't have to go with a new tc.
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  #6  
Old 03-07-2014, 04:18 PM
lv740il lv740il is offline
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Also would a bad torque converter throw the code at initial start or after the car is put in gear and driven?
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  #7  
Old 03-07-2014, 05:22 PM
hermosan hermosan is offline
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p0740

Sorry to sound so melodramatic. Today is the second full day of driving the car with the new noise. Which at driving speed is negligible. It seems to be shifting okay, no power loss, gas mileage is 16.9 mpg in L.A.driving. No codes popping. Before replacement cel would light up after 20 or so miles after erasing . I probably would have replaced the solenoid during the trans service but didn't . There are so many things to replace on these cars that you might wait until they fail first so you can keep up as you go along. With the weekend coming I am going to dig into the problem. good luck
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  #8  
Old 03-07-2014, 07:04 PM
CitizenOfDreams CitizenOfDreams is offline
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Just to clarify...

Code P0740 means a very specific condition - "torque converter solenoid circuit open". That is, either bad solenoid, or bad wiring between the gearbox and the transmission control module. (Or bad transmission module, but that's probably less likely.) I cannot imagine a mechanical or a hydraulic problem causing this particular error code, no matter what transmission shops or Internet gurus may say.

Same thing with the speed sensor: if the diagnostic shows the specific "circuit open" error, that means exactly what it means: no continuity in the sensor circuit.
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  #9  
Old 03-08-2014, 09:55 AM
hermosan hermosan is offline
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Internet Guru?

I'm sorry to contradict your wisdom on the p0740 code. I am in no way a bmw expert, but internet research involves real people trying to solve real problems they have fixing these complicated machines. In many cases(like mine) they don't have fat wallets to buy new warranteed vehicles. Even new beemers are constantly in the shop as evidenced by the number of loaner cars I see on the roads. If newbie wants to change his tc solenoid he should do so. I hope that cures his tranny issue. I have seen where many 740 owners have swapped out solonoids to no effect. I am convinced my TC was bad. I replaced it. Another problem cropped up. No big surprise. Let's see if Newbie get's it sorted so he can move on and address the myriad other repairs that await. thanks for your input.
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  #10  
Old 03-08-2014, 10:38 AM
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FABOCH FABOCH is offline
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dont know if the majority of transmissions are created equal or not but I have a 2000 DoDge Durango....It had a bad transmission governor solenoid...It would hiccup and throw itself into safe gear plus the CEL light on dash would appear as well as transmission overheating warning....Replaced the solenoid, which was an easy swap and the tranny is running like a champ...Hopefully u can just swap out the bad solenoid and its an easy fix
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  #11  
Old 03-08-2014, 12:45 PM
CitizenOfDreams CitizenOfDreams is offline
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Quote:
Originally Posted by hermosan View Post
I'm sorry to contradict your wisdom on the p0740 code. I am in no way a bmw expert, but internet research involves real people trying to solve real problems they have fixing these complicated machines.
I would take the Internet wisdom with a grain of salt (my own advices notwithstanding).

Some of those people have never truly solved their problems, or solved them by "throwing parts".

Some of those people had a different problem, so their advice is valid but not applicable in your case.

Some of those people got their information from, well, the Internet.

And some of those people plain don't know what they are talking about.

Quote:
In many cases(like mine) they don't have fat wallets to buy new warranteed vehicles.
That is precisely why you need to think, test, measure and investigate before you take a wrench and start swapping expensive parts. Car repair by "throwing parts" can get real pricey real quick.

Quote:
If newbie wants to change his tc solenoid he should do so. I hope that cures his tranny issue. I have seen where many 740 owners have swapped out solonoids to no effect.
You are totally misreading my advice. I am not suggesting to grab a wrench, drain $200 worth of transmission fluid and swap a $100 solenoid.

I am suggesting to find out why the TCM is complaining about open circuit. It can be bad solenoid, or it can be as simple as a broken wire at the transmission connector. You need to find out what is it and fix it. After you have that problem solved, see if you have any other errors/problems and investigate them.

Last edited by CitizenOfDreams; 03-08-2014 at 12:46 PM.
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  #12  
Old 03-10-2014, 06:45 PM
lv740il lv740il is offline
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Just called the dealer and they don't have or know what the torque converter solenoid is. It shows that there is a speed sensor in the bell housing and 3 sensors in the valve body. The tech informed me that I might need a new torque converter or a whole new transmission. The hoa would **** a brick if I dropped my trans, I'm guessing the only way to check the solenoid and wiring is to pull the pan? I know the transmission and torque converter are still good according to what I have read about getting full lock on the highway.
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  #13  
Old 03-10-2014, 07:37 PM
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FABOCH FABOCH is offline
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Im for the SIMPLE FIXES...Pull Transmission harness OFF...SPray Electrical cleaner spray CRC makes is..$6 range....Let it dry , reconnect harness and drive her...See if she acts up again,,,,,Also Clean the ABS Speed Sensors.....They have a tendacy to build up gunk at the tips of the sensor heads......Simple cleaning solution(soap water) or glass cleaner (what I use)
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  #14  
Old 03-10-2014, 07:52 PM
lv740il lv740il is offline
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Thank you fab! I will be doing this first. Hope it fixes it, I'll report back in a couple days
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  #15  
Old 03-24-2014, 06:41 PM
FreeMW740IL FreeMW740IL is offline
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Just put a used tranny in my 740... tranny is great, but on the second day driving I got the no lock up and tcc code 0740. Going to slap a new LUC solenoid in it and see if the torque converter gets the pressure it needs to lock up. I am using Febi Bilstein ATF Ill post pics and success/failure stories soon... Ive been stacking them up!!
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  #16  
Old 03-24-2014, 11:27 PM
lv740il lv740il is offline
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Luc solenoid? Car is going to the shop this week. =(
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  #17  
Old 03-27-2014, 08:51 AM
FreeMW740IL FreeMW740IL is offline
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The lock up solenoid can be easily swapped out by dropping the tranny pan. Easy. Problem is the plastic clip for the plug will most likely break since it's been heated so any times, the plastic becomes brittle.


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