More E39 Questions
 

Did some searching on the bimmer forums, but found very little info.

Earlier today, my E39 flipped into "Trans Failsafe Program" at a stoplight. I had to limp back to my office in 3rd gear. A few hours later when I left work, I started the car back up and the trans failsafe message had gone away but my Service Engine soon light came on. I stopped at Autozone on the way home and had them run the code.

It came back as P0721 -Output Speed Sensor.

I drove carefully all the way home and tried to notice anything that felt off about the way the car was driving but I did not feel anything. My quick research indicates that this could be a bad sensor, a sign of low transmission fluid, an actual problem with the transmission, or even possibly a bad battery/alternator that is messing with the trans codes.

Anybody with help or experience here? Clearly I am going to need to get this to the shop and have it looked over. My family uses a small shop in the suburbs for most of our work and the mechanics/owner seem straightforward and honest, but I still like to know what direction my wallet is heading before I drop the car off.

Thanks in advance.

How many miles are on the transmission?

Sorry...2002 -84k miles

i have an e36 . did the gear amber idiot light come on? try disconnecting the battery if it did, it will clear the codes but sooner or later the code will come on everytime. mine turned out to be the control box, there's an chip in there that messes up.

Down the toilet. It's a BigMoneyWaster. I love my 540 E39 though regardless of $$$$$$$$$$$$$$$pent.

I was having trans problems on my E39 2002 530i with about 85K mi. It was slipping on starting from a stop, and not shifting crisply. No warning lights. local shop said to rebuild or replace trans. this is said by factory to be a no service trans.
After reading up on the issue I decided to replace the fluid and filter in the trans. the problem cleared right up. Whew!!
Not sure if this is the answer you need but may get you looking in the right direction.
There is some info here on the BMW forum, and on bimmer fest Forum.
Good luck with yours.

Cheers Richard

Most likely you have a clutch-pak starting to fail /slippage - not speed sensor as the input shaft speed is 'reading' different than output in high gear. There may be some saving grace if this just occoured - locate a good independent BMW shop, If no other choice - Dealer. If independent, make sure the shop MUST have either (at least) GT-1 or a Autologic scan tool to properly diag. Make sure you ask this question. Any other scan tool is a waste of time.

It IS possible that the speed sensor has actually failed or the trans has been leaking fluid and had finally got to the point of low fluid level causing slip.


PM me if you need to discuss further..........

Update: driving today for work, SES light went away.


Gambler, I will likely reach out later today.

Ok, back in front of a computer where I can type. Driving a little bit for work today, the SES light went off.

Besides the recent trans code, about once every 2 weeks, the radio will shut off on its own or the display will flicker and pulse with the beat of a song. In addition, the abs/DSC lights will randomly light up and then go away, sometimes after just a few seconds and sometimes after I turn the car on and off.

From research, these electrical gremlins are likely caused by a bad ground or a bad ignition switch. Any chance that it is also playing with the transmission.

Asphaltgambler, pm sent.

I’ve put 110k on my E39 M5 and I’ve never encountered any problems like that. It almost sounds like 2 different problems. One clutch related and one electrical. Did you try the asking the question on the M5board?