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Output speed sensor malfunction, trans failsafe mode

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162K views 32 replies 25 participants last post by  chaquis990  
G
#1 ·
I am having problems with my 2003 4.6is. It is continually throwing a P0720 OBD code for the output speed sensor. When that happens it slams the trans into failsafe mode. Happened the first time 6 months ago in very cold weather then not again until recently but lately every day. The X5 just had a 2 week holiday at the local BMW store, all they could do was change the trans fluid, which hasn't had much if any effect. Of course, they are wanting to change the whole tranny but on driving it does not slip in any gear and feels very solid. There are 62,000 miles or 100,000 km on the X5, just recently off warranty.
Until now little or no problems, but this one they can't seem to fix!

HELP
 
C
#2 ·
Same problem trans failure

Same issue. I noticed my problem when I would be at a dead stop and mash the gas to the floor. The trans felt like it was slipping or limp mode. The only way I could get the truck back to normal operating condition was to turn it off and restart it. Then all was well. The dealer also told me and quoted me for a new trans $7000.00 plus labor. I did my own research and came up with my own conclusion of the OUTPUT-SPPED SENSOR needs to be replaced. I think I have found enough info to support this. I will let you no how I make out this week when I change it. But below is what the computer at the BMW dealership spit put.

49 Gear monitoring
Fault is the 1th fault to be detected.
Output-speed-sensor signals not sent or too high level of slip in the gearbox.
Implausible signal
Fault currently present.
Fault not sporadic.
Last gear shift: Upshift 2-3
ATF temperature: 19degrees C
Output speed: 736rpm
 
M
#26 ·
output sensor

chris1 said:
Same issue. I noticed my problem when I would be at a dead stop and mash the gas to the floor. The trans felt like it was slipping or limp mode. The only way I could get the truck back to normal operating condition was to turn it off and restart it. Then all was well. The dealer also told me and quoted me for a new trans $7000.00 plus labor. I did my own research and came up with my own conclusion of the OUTPUT-SPPED SENSOR needs to be replaced. I think I have found enough info to support this. I will let you no how I make out this week when I change it. But below is what the computer at the BMW dealership spit put.

49 Gear monitoring
Fault is the 1th fault to be detected.
Output-speed-sensor signals not sent or too high level of slip in the gearbox.
Implausible signal
Fault currently present.
Fault not sporadic.
Last gear shift: Upshift 2-3
ATF temperature: 19degrees C
Output speed: 736rpm
Click to expand...
How did this turn out?
 
K
#3 ·
i'm having the same problem

i just got the car last week the second day it was slipping the third day it left me stranded it gave me the code P0720 now the car does not run does someone know for sure if by replacing the output speed sensor the car will run, i have a 328i cabriolet.

one more thing does any one know how to get the top to work it stopped working.
 
E
#4 ·
Found this I'm going to try it if it helps my batmobil.

DTC:
P0721

Fault Description:
Output speed sensor circuit malfunction

Monitoring Conditions:
Drive vehicle in forward gear >15 mph (25 km/h)

OBII
No

Check Engine:
No

Other:
No

Default Action:
When fault is detected:
***8211; TCM substitutes rear wheel speed for transmission output speed (via CAN) (This fault is not detectable by driver.)

Possible Cause:
- Transmission to TCM output speed sensor circuit open circuit, short circuit or high resistance
- Transmission to TCM output speed sensor circuit shielding defective
- Transmission internal output speed sensor circuit open circuit, short circuit or high resistance
- Output speed sensor failure

----------------------

Transmission Output Speed Sensor:
The output speed sensor provides the TCM with transmission output shaft speed information. This signal is produced from an inductive pick-up, generating 36 pulses per revolution.

The transmission casing:
- Houses the geartrain and electro-hydraulic control unit.
- Contains the input speed sensor which measures turbine speed.
- Contains the output speed sensor which measures the transmission output speed.
- Contains the hydraulic system pump.
- Contains the fluid temperature sensor.

Output Shaft Speed (OSS) Sensor:

Removal:
- Open the driver's door, or both doors if necessary, to allow the side glass to drop.
- Ensure that the doors remain open until after the battery has been disconnected.
- Disconnect battery ground cable.
- Remove the battery cover.
- Raise the vehicle on a lift.

Warning: TRANSMISSION FLUID MAY CAUSE SEVERE BURNS, ENSURE THAT ALL SAFETY PROCEDURES ARE OBSERVED.

- Carefully remove the drain plug and drain the transmission fluid.
- Remove the twenty-two bolts which secure the fluid pan.
- Remove the fluid pan and all traces of gasket material.
- Remove the output speed sensor.

Note: M6 fixing.

- Disconnect the multiplug from the speed sensor.


Installation:

Note: M6 fixing.

- Connect the multiplug, install the output speed sensor and securing bracket. Tighten the screw to the specified torque figure.

Note: Ensure extreme cleanliness and never reuse transmission fluid.

- Using a new gasket, install the fluid pan and tighten the twenty-two fixings to the specified. torque figure.

- Perform the Battery Reconnection Procedure described in Operation 86.15.15.

- Refer to (44.24.02) for fluid fill procedure.
 
K
#6 · (Edited)
Several Items could be the problem

My 1993 325is has the same condition, it will also go into fail safe after a hard acceleration. I was told by the BMW dealership that my eprong had to be changed, it is located inside of the TCU, They wanted to charge $1800 for the labor and the part only cost $20.00 after the removal of the TCU from the vehicle it took only 5 minutes to install eprong. I ordered the eprong and replaced it myself, after doing so it continued to exibit the same conditions so I took it back to the dealer again. I was told by the dealer today that I could have three (3) conditions that could cause the problem.
#1. Replace the Out put in put speed sensor
#2. Check the Wire Harness on the top of transmission for shorts
If the above two do not take care of the problem go to #3.

#3. The internal functions of the transmission must be repaired.

My next move is the #1 Replace the output, input sensor.
 
A
#8 ·
Output Speed Sensor replacement

I've been on the E46 site on a similar thread. It seems no one has tackled or reported back on the sensor replacement. I'm going to say I'm planning on getting this done within a week since I have the benefit of having a Qwiklift, but being that it is winter - no promises. I'll report back. I sure hope this does it. I've been living with this slipping and then stuck in 3rd gear issue for more than 6 months. It is only recently that I got the code for this. Befor that it was only the one that said something like improper gear ratio (don't recall the #).
 
Y
#9 ·
guys the purpose on posting your issues on the forum is also to come back and give us updated please.

without keeping us update how do you want us to improve or to get the solutions.

thanx in advance.

now back to our topic

my car had a lot of light on the dashboard just like a christmas tree. ABS/DSC/BRAKE, engine failsafe came on, what i did was stoping the car and restarting it all was gone and engine eas runing fine even did a 300 km trip cruising at a maximum speed of 100km/hrs was to scared to get the message back i realky hate the feeling of might be getting the messge agin. then when i came back to town i went to my friens garage and we did a OBDII chabk and got a couple of message when of the said that the throttle body acctuator was jammed kind of felt that was the problem cause i remember when i was in a stop the rm just went above 1500 rpm and stayed there for 30 seconde was so weird my wife told me that the car was going coucou :eek:uch:. by the way when i got the message of engine failsafe we pull the car aside and noticed that the rpm was also stucked for a minute into 1500 rpm even i park mode, so after waiting fo a minute we just switch off the car and all gone.

to go back to what happened with my mechanic we just replaced the trhottle body with a used one from the junk yard and we also noticed that the old one was kind of broken ( plastic cover) he also reminded me that we did have a message regarding the TBA 3 months ago so that was really making sens to me.

drove the car another 200 km away just to test drive you know all kind of speed nothing to signal just that the car was feeling a beet slow for an x5 if you know what i mean.

finally once out of the motor way i give the car a bit of acceleration from a dead stop first time the car was to slow to respond said ok lets try a se onde time still to slow i was slaming the accelerator man, the third try the trans failsafe message poped up i park switched off the car and restarted imediatly nothing all gone i drove the car back home 200 km nothing car drive good but i really have to accelerate slowly should not drive brutally. man thats sh*i i didnt buy a bmw to drive like a f***ing corolla. so now im really trying to find out whats wrong the transmition is a new rebuilt so no F****ing way even the throttle body was replaced by the garage under waranty so now we are thinking sensors a moduls abs dsc or speed sensors theire must be something wrong somewhere that trigger this fault but what.

my aim here is not to just repair the car butbto make it run perfect and for good like a bmw " ultimate driving machine " need your help guys lets put our hands together on this and get a permanet solution for eveybody afterall its only machines and there is nothing in this world that cant be repaired. im decided not to sell this car ill fight till the end.:irate:
 
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S
#10 ·
Ok I have tried to do all my research before I posted up in here, but I honestly could not find a clear, definite answer to my issue. Here is the deal:

I have 2000 323ci. 8/10 times when I accelerate up a hill, go 60+mph, or drive for more than a few minutes a gear light with an exclamation mark in the middle of it will appear on my dash beside the Park/Reverse/Drive light. As soon as that light appears the tranny will jump into either 3rd or 4th, cant really tell which though I think its 4th, and literally be STUCK there. No matter how fast or slow I go after that light appears, the tranny will be in 4th gear. I can come to a complete stop, then accelerate and its in 4th gear which makes for an extremely sluggish acceleration. I can be going 80mph and be forced to run over 4000rpm while stuck in 4th. However, once I kill the engine for about 1 minute, the care resets and I can drive normally again, well that is until the light comes back on.

I took it to a European AutoSport garage and they scanned for codes. The result they told me is as follows: "Trans. has codes for the input and output speed sensors internally and the #3 shift solinoid--Approx $700 to replace parts and service transmission."

I also asked one of the guys on gixxer.com who used to be a BMW tech what he though and replied as such,"BMW does not offer (many) replacement parts for transmissions, they usually just replace the whole trans. With three codes you would have to figure out which one is causing the problem and which is just a result of the other problem. Is a bad speed sensor causing the shift solenoid to not act right? or is the solenoid causing the speed sensor codes? Basically if its the shift solenoid, and you can not get that aftermarket, you're screwed."

So does anyone here have any clue what this is, if it is fixable, any experience with this issue? Any help is appreciated. Thanks guys.
 
#12 ·
Speed&ThankYou said:
Ok I have tried to do all my research before I posted up in here, but I honestly could not find a clear, definite answer to my issue. Here is the deal:

I have 2000 323ci. 8/10 times when I accelerate up a hill, go 60+mph, or drive for more than a few minutes a gear light with an exclamation mark in the middle of it will appear on my dash beside the Park/Reverse/Drive light. As soon as that light appears the tranny will jump into either 3rd or 4th, cant really tell which though I think its 4th, and literally be STUCK there. No matter how fast or slow I go after that light appears, the tranny will be in 4th gear. I can come to a complete stop, then accelerate and its in 4th gear which makes for an extremely sluggish acceleration. I can be going 80mph and be forced to run over 4000rpm while stuck in 4th. However, once I kill the engine for about 1 minute, the care resets and I can drive normally again, well that is until the light comes back on.

I took it to a European AutoSport garage and they scanned for codes. The result they told me is as follows: "Trans. has codes for the input and output speed sensors internally and the #3 shift solinoid--Approx $700 to replace parts and service transmission."

I also asked one of the guys on gixxer.com who used to be a BMW tech what he though and replied as such,"BMW does not offer (many) replacement parts for transmissions, they usually just replace the whole trans. With three codes you would have to figure out which one is causing the problem and which is just a result of the other problem. Is a bad speed sensor causing the shift solenoid to not act right? or is the solenoid causing the speed sensor codes? Basically if its the shift solenoid, and you can not get that aftermarket, you're screwed."

So does anyone here have any clue what this is, if it is fixable, any experience with this issue? Any help is appreciated. Thanks guys.
Click to expand...
HeyI was just looking around and just thought I'd pass info just in case anyone was wondering, or didn't know. if you go to www.thectsc.com They sell ZF Original Transmission Parts. The parts that most are looking for. Hope this helps someone out. Later!:thumbup:
 
M
#11 ·
Transmission Fail Safe causes un-related to actual code shown on diagnostic computer

I've had some recent experience with "Trans Fail Safe" in my 2003 X5 4.4 that may be helpful.

The bottom line is that the codes are not always \ ever correct. In my case, kept getting the P0720 "Output Speed Sensor" as cause of the fault code. We replaced the Output Speed Sensor and that did not fix the problem.

In my case, the Trans Fail Safe code came on when indicated speed passed 80mph...and only when trans fluid was hot - maybe 30 minutes plus highway driving. And, it was not a faulty indicator light - the tranny was clearly shifting into the "limp home" mode. But, all I had to do was pull over to side of the road , turn engine off, wait 10 seconds and crank it back up - light was out and tranny was back to normal ops.

So, we conclude that the failure was heat-related in some way. New fluid had no effect, so I changed the transmission oiler cooler (a pretty easy do-it-yourself project...no special tools needed...just a couple of clamps to release). That cured the problem. Part is less than $200 online.

So two points here. First, the codes are often not accurate. Second, many codes will be triggered by transmission fluid-related issues...either fluid & filter need changing or the cooler. Per a couple of mechanics I have spoken with, they are convinced that the trans oil cooler needs to be replaced by 100k miles, if not sooner. For the life of me I could not figure out why this worked, because the cooler appears to have no moving parts - I cut it open to see if there are any valves or sensors inside, and there are none. Nor did its internal coils appear to be clogged up. But all I know is that the new cooler fixed the problem immediately, with no further recurrences after extensive subsequent miles.
 
B
#21 ·
M3flyboy said:
I've had some recent experience with "Trans Fail Safe" in my 2003 X5 4.4 that may be helpful.

The bottom line is that the codes are not always \ ever correct. In my case, kept getting the P0720 "Output Speed Sensor" as cause of the fault code. We replaced the Output Speed Sensor and that did not fix the problem.

In my case, the Trans Fail Safe code came on when indicated speed passed 80mph...and only when trans fluid was hot - maybe 30 minutes plus highway driving. And, it was not a faulty indicator light - the tranny was clearly shifting into the "limp home" mode. But, all I had to do was pull over to side of the road , turn engine off, wait 10 seconds and crank it back up - light was out and tranny was back to normal ops.

So, we conclude that the failure was heat-related in some way. New fluid had no effect, so I changed the transmission oiler cooler (a pretty easy do-it-yourself project...no special tools needed...just a couple of clamps to release). That cured the problem. Part is less than $200 online.

So two points here. First, the codes are often not accurate. Second, many codes will be triggered by transmission fluid-related issues...either fluid & filter need changing or the cooler. Per a couple of mechanics I have spoken with, they are convinced that the trans oil cooler needs to be replaced by 100k miles, if not sooner. For the life of me I could not figure out why this worked, because the cooler appears to have no moving parts - I cut it open to see if there are any valves or sensors inside, and there are none. Nor did its internal coils appear to be clogged up. But all I know is that the new cooler fixed the problem immediately, with no further recurrences after extensive subsequent miles.
Click to expand...
It seems that no one paid attention to what you wrote for some reason and the funniest part is that YOU'RE SPOT ON!

The same things happened to my car, changed fluid, filter, gaskets, harness, bolts, the monkey inside of the trans pan, and none of these fixed the issue, so I plugged the scanner and went for a ride until the problem was triggered again, slam, limp mode, etc. What I saw in INPA was that temperature was way too high when it happened (over 140° C or 284° F). It was that much that you could sense your legs hot.

Well, long story short, Heat Exchanger (Oil Cooler) was... well, in my case was absent at all (a butcher that calls himself a mechanic get rid of it bc it was not working). So, I bought a new one, changed filter again, fluid and voila, haven't had a single issue since then (about a year ago).

I was told that I needed a new transmission, but a friend of mine told me it couldn't be that bad, so I listened to him and my guts and it paid off.

Try that first. These transmissions are way too good, but the cooling system is not, and they all suffer bc of this.
 
T
#13 ·
I'm having a similar issue with my 2002 BMW X5 4.6is. The transmission shifts fine once i'm driving on the highway, but once i slow down to around 5 - 10 mph the transmission shifts to neutral. If i'm on a decline the transmission re-engages once i get up to around 15 mph. i'm thinking that the transmission output speed sensor is bad and it's substituting wheel speed for transmission output speed like @elma22 said. I have both sensors plus the harness and i'll change these in a few days and post results.
 
U
#14 ·
thudderman, any improvement after you installed the two speed sensors and the new harness?

I just bought a 2002 X5 4.4i, at an auction, I got a good deal so I am ok that it is having some issues.

I got a P0720 Output Speed Sensor code as I drove it home (frustrating because I scanned for codes before I bid on it, they cleared the codes). I noticed that when taking off from a stop it revs quickly, moves slowly, and then slams into gear. This feels like you are being rear-ended, not cool. I only drove it home, and a few short times very close just to diagnose it. Once it is over 10-15 MPH it runs fine, and the shifts are smooth, I can even use the Manual shifting mode. However if I floor it and it downshifts, it will rev up and slam into gear even when going 40 MPH. Then it goes into Failsafe mode and the Manual shifting is no longer available.

I just changed the Rear output sensor, filter and fluid, no difference.

It is parked until I can find something else to try. I may have to pull it and rebuild it, I see there is some good info on how to do that. I would like some confirmation that it is required, and not just something else electronic causing it to fail.
 
T
#15 ·
JaredT,

Which speed sensors did you change? Was it the ones in the transmission or did you change the rear wheel speed sensors? I haven't gotten around to changing mine in the transmission as yet, as I have been extremely busy. As soon as I do I'll post results.
 
#32 ·
T
thudderman said:
JaredT,

Which speed sensors did you change? Was it the ones in the transmission or did you change the rear wheel speed sensors? I haven't gotten around to changing mine in the transmission as yet, as I have been extremely busy. As soon as I do I'll post results.
Click to expand...
He ones in the transmission aren't that hard to change. You should have two an input and output. It's best to change both and the filter. Took me about 30 minutes with power tools they are easy to get to after the pan is removed.
 
M
#18 ·
I just replaced output shaft speed sensor for code and at 25 mph it shudders searching for gear otherwise is fine. It was doing it at 35 mph prior to trans reset when it went into limp mode. Key to on position, throttle to floor for 40 seconds, start and drive forward only. Anyways still have the searching for gear at 25 mph. Grrrrrr
 
#20 ·
Eric Grier said:
could anyone tell me where is the transmission speedsensor. Please
Click to expand...
Eric, it depends on the model. Some people look for similar issues in other model forums. Let the forum know the year/model of your Bimmer.

The output speed sensor is located in different places depending on the model. For example, I have. 2004 E60 and it's located on the mechatronics unit. However older 5series Bimmers it's located outside the tranny case. I wish I still had a picture saved for you, but there is one somewhere on this site. Sorry I wasn't much help.
 
B
#24 ·
INPA will tell you what's the temperature of your transmission fluid for sure and yes, the thermostat is set to open at 82°C. In normal conditions my transmission runs between 80° to 95°C when it gets really hot.
 
F
#28 ·
can anybody help me?! my 02 x5 with 4.4i is having tranny issues it wont shift outta 2nd gear its an auto trans! could it b speed sensor??? already did tranny tune up filter fluid etc cooler thermo etc does anybody know????? pls help!!! it has 118000 on it
 
A
#29 ·
I have problem with my car x3 e83 it was good then I saw the oil dropped under it I repair it and changed the oil and filter for transmission but the proplem is still exist the 3rd gear doesn't move to 4th and the sign light up in insturme the code in diagnostic was 5565 EGS turbo charger. speed sensor
Any help my friends

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