Trans failsafe prog with no prior signs of trans issues e39 98 540i help please

[danthedanimal]

Ok so my 98 540i has about 170k on it but the transmission has been running smooth as hell since I bought it. I hadn't noticed any slipping or anything and I've put some decent miles on it since I bought it. While going up a hill this past week it suddenly didn't want to shift then popped the trans failsafe prog on the dash. I was barely a mile from my house so I made it home in that limp mode. I started with changing the transmission filter and fluid. Not surprisingly that didn't solve the problem. Basically when you start it up and put in drive and hit the gas it behaves as though it's in park, then trans failsafe pops up on the dash, and eventually it will move but not easily which makes sense since based on my research it's stuck in either 3rd or 4th gear while in failsafe. I used a basic scanner on it and it's giving me the following codes:

-p0720 output speed sensor
-p0733 gear 3 incorrect ratio
-p0731 gear 1 incorrect ratio

I recently scanned it for a check engine light which I solved with replacing the oxygen sensors and these codes were not there at that time. They showed up suddenly out of nowhere at the same time as the trans fail safe prog.

When I I changed the the transmission filter and fluid I did find three metal shavings in the pan about the size of an aspirin

2018-06-16 14.17.14.jpg



I have two theories one is that my transmission is ??? and It needs to be rebuilt or replaced. My other theory is that that there is an issue with the solenoids. I figure their has to be a way to test the solenoids with a volt meter but I'm not really sure where they are or how exactly to do that.

Any ideas or hunches? I just think it would weird for my transmission to go from running great to being toast with no warning so that's why I'm thinking this is fixable without replacing/rebuilding transmission.

[1823alex]

Personally, when I got trans failsafe prog it was actually my alternator since the alternator would short out to the casing and spike from 12 volts to about 17 - 20 volts and then it would limp mode.

Although it doesn't sound like that's the case for you as it happens as soon as you start the car and stuff.

Probably gonna need to rebuild it or something.

[toybreaker]

Check the sensor/switch attached to the shift shaft going into the transmission. if the wiring is boogered at all it will cause the fail safe condition. (wet weather really helps it go south)

[danthedanimal]

Alternator and battery is good. I've ruled that out, but not whether it's electrical or mechanical. Thanks for the input. Just got the bentley manuals for my car and ordered a foxwell nt510 scanner so I'm gonna go all in on this. I bought this car as a project and already put the as much money into it as I paid for it, replacing or upgrading stuff on it, So it's too late to turn back now, Whenever I fix it or replace/rebuild it, I'll probably post a new thread about it.

[crazy4trains]

Alternator and battery is good. I've ruled that out, but not whether it's electrical or mechanical. Thanks for the input. Just got the bentley manuals for my car and ordered a foxwell nt510 scanner so I'm gonna go all in on this. I bought this car as a project and already put the as much money into it as I paid for it, replacing or upgrading stuff on it, So it's too late to turn back now, Whenever I fix it or replace/rebuild it, I'll probably post a new thread about it.

Are you sure? Post your voltages with car off and with car running. Measure voltages at battery if you can.

[Panzh]

Any updates? I’m having the trans fail safe myself, can someone see my post and see if you can figure out what’s going on?

[phastkat]

Just posted this last n another thread, maybe it’ll help you too...
A few years ago I kept getting the fail safe mode for reasons I can not explain. Everything on the car was working fine, including the transmission. I checked/changed various sensors, looked for shorts, checked electric currents and draws, and even changed the computer, but to no avail. Eventually I read that the problem could be caused by a bad solenoid on the shifter, so I removed the shifter to take the solenoid off only to find that on the 2003 540i the solenoid can’t be replaced without replacing the entire shifter. So, I changed the shifter, but still no luck. Not convinced the problem wasn’t related to the solenoid, I taped down the shifter locking pin that comes out of the solenoid and I did not have a fail safe message again. I can’t tell you why that worked, but only that it did.

[tonytwoseams]

i got this.. noticed my brakes were a bit squeally and it happens when the gearbox got hot.. could smell burning or hot fluid.. took like 2 hours of driving from cold to happen..

[JimLev]

Hey noobie, I've got a theory too, you need to read the rules so we don't bounce you off the forum, OK.
All the Rules are at the top of the page, this one is worth remembering.....

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[kouks]

Your A drum has ruptured.

Those parts are not shavings, they are the part of the drum that keeps the drum brake retaining ring in place, the ring has slipped and the trans will no longer hold 1st gear. The reason you are getting a 3rd gear warning also is that gears 1-3 are nested together in a group. Since gear 1 has failed, it is affecting the operation of gears 2 and 3, in this case, 3 is the one affected. The fact that the output speed is also coding confirms the gears are gone. The input and output speed sensors compare each others rotation and when the difference is too great, then the gears are either slipping too much, or not producing the required torque, which is your case.

The 5hp24 is known for blowing the A drum (1st gear) and at 170k miles, yep, its about time.

Sorry, I've had two 5hp24 explosions, one was the A drum, the other was the reverse drum (F).

For all TFS codes, here's the basic process:

1. Check the battery voltage first, should be over 12v cold, and over 14v running (about 14.1 or .2). The trans is very sensitive to voltage, so any anomalies can cause a TFS. If the battery is old and weak, replace it. If the voltage while the car is running is way too high or low, or eratic, the alternator is to blame, and most likely just the voltage regulator on the alternator, but at that point, replace the whole thing. If battery and alternator are fine...

2. Clear all codes with INPA or another program (or disconnect both battery leads for about 10 mins), and see if the codes repeat themselves.

2a. If the car seems to drive OK after deleting the codes, then its most likely an electrical issue. Check all connections, clean and reset. You can use newTIS.info to look for the pinouts of the trans connectors or use INPA to activate the solenoids in the trans individually (with the car NOT running) and try to find a bad solenoid or bad speed sensor.

2b. If the trans goes into TFS fairly quickly again and presents the same codes, then you most likely have a mechanical failure and you need a plan a replacement or rebuild. You could be lucky and it be a torque converter problem, or ruptured a drum and a complete rebuild is due.

In general, if the codes or problems are repeatable, its a mechanical failure, if they are sporadic or presents itself in various ways, its most likely electrical.

Changing the fluid and filter may work, but will only delay the inevitable, not fix it. Fluid and filter changes will work only at the initial onset of anything strange as far as gear shifting, and only if its a benign issue, not anything significant.

[c00k]

So I have the same code p0720 but none of the other ones. But I do have the code p0443 that show up also.

My question is do you believe that I have the same problem with my A drum bring ruptured? I’ve changed the output speed sensor and still the code p0720 pops up. I didn’t have no pieces of metal in my trans box like his. But when I do start up my car and put it in drive it’s stuck and won’t move until the car goes into TSM and then I can drive but stuck in 3rd gear. Please help any info from you would be great! Thanks

Your A drum has ruptured.

Those parts are not shavings, they are the part of the drum that keeps the drum brake retaining ring in place, the ring has slipped and the trans will no longer hold 1st gear. The reason you are getting a 3rd gear warning also is that gears 1-3 are nested together in a group. Since gear 1 has failed, it is affecting the operation of gears 2 and 3, in this case, 3 is the one affected. The fact that the output speed is also coding confirms the gears are gone. The input and output speed sensors compare each others rotation and when the difference is too great, then the gears are either slipping too much, or not producing the required torque, which is your case.

The 5hp24 is known for blowing the A drum (1st gear) and at 170k miles, yep, its about time.

Sorry, I've had two 5hp24 explosions, one was the A drum, the other was the reverse drum (F).

For all TFS codes, here's the basic process:

1. Check the battery voltage first, should be over 12v cold, and over 14v running (about 14.1 or .2). The trans is very sensitive to voltage, so any anomalies can cause a TFS. If the battery is old and weak, replace it. If the voltage while the car is running is way too high or low, or eratic, the alternator is to blame, and most likely just the voltage regulator on the alternator, but at that point, replace the whole thing. If battery and alternator are fine...

2. Clear all codes with INPA or another program (or disconnect both battery leads for about 10 mins), and see if the codes repeat themselves.

2a. If the car seems to drive OK after deleting the codes, then its most likely an electrical issue. Check all connections, clean and reset. You can use newTIS.info to look for the pinouts of the trans connectors or use INPA to activate the solenoids in the trans individually (with the car NOT running) and try to find a bad solenoid or bad speed sensor.

2b. If the trans goes into TFS fairly quickly again and presents the same codes, then you most likely have a mechanical failure and you need a plan a replacement or rebuild. You could be lucky and it be a torque converter problem, or ruptured a drum and a complete rebuild is due.

In general, if the codes or problems are repeatable, its a mechanical failure, if they are sporadic or presents itself in various ways, its most likely electrical.

Changing the fluid and filter may work, but will only delay the inevitable, not fix it. Fluid and filter changes will work only at the initial onset of anything strange as far as gear shifting, and only if its a benign issue, not anything significant.