S65/S85 throttle actuators - electrical failure SOLVED

[V8FunNaturally]

Bravo ! This thread should be a sticky.

That gear should have been metal alloy not some children toy PTFE gearing
it would not file if it's not the cheapest steel. And they could have compartmentalized the board anyway.

If bmw had any decency they would cover all throttle actuator failure on the car regardless of warranty. This clearly exposes a poor choice of material or wrong torque electric motor choice by the subcontractor who makes those for bmw.

[jdamore]

Its real important to get solder to flow entirely under that chip when installing the replacement so you have good heat transfer.

First thing to come to my mind when transistors are over heating is heat sink! Even if it's just a metal plate. Good find.

Did you have any signs early on that it was going to fail?

Are the gears greased?

[Flea7]

Originally Posted by jdamore

I
Did you have any signs early on that it was going to fail?

For me it was gradual. First, Increased Emissions...about a 2 months later I would go into a limp mode.....not while driving but when starting the car.
I could generally reset by turning the car off and on. It will get more frequent until you cannot reset by doing that.
When my car when into limp mode while on the road is when i decided it was time to replace them.

I have a code reader and both my actuators was throwing error codes that also triggered other codes as well.
I replaced #1 and then replaced #2 about 2 weeks later.

I replace them myself with the help of ///M DIY. 2 actuators cost me $1550.00..cheap considering the dealer wanted around 4k.

[tenman]

Oh wow. Nice find! Has anyone replaced the gears?

[Merlin_83]

Greetings,

1st off - dude, very impressive taking on a task like this and fixing/resolving the issue replacing the FET's on the PCB from the car, I am very comfortable soldering, even very fine pitch stuff - like surface mount MCU's with tons and tons of pin-outs, but I would be freaking out working on an actual greenboard from my M3 . And those FET's look massive in size too ! I was really surprised you were able to source them from Digi or Mouser as well.

Regarding the comment that people are making there own gears, that has to be getting done with 3D printing, yes ? And if so, why did the factory not use some fancy high plastic compound that would not wear like these did ? Can 3D printers place higher or better quality plastics then OEM?

And, I read your post a couple of times and examined the photographs for some time, my question is this; why or how come the FET has burned out ? And the other FET adjacent to the one you replaced, what is it's function ?

When do the throttle actuators shown signs of trouble ? At a certain mileage ? Or particular model years ? Again, very well done sir !! These kinds of informative posts are really great !


Cheers,
Merlin

[Acree]

Very well done! As a EE, it's nice to see someone finding the actual source of the problem and not just bending over the barrel. I have this post bookmarked now. Thank you!

[Beemdog]

I believe the OP mentioned that it is possible the excess backlash in the worn gear teeth causes the actuator to constantly "hunt" for position when set in that spot. This could lead to the overheating of the motor driver FETs.

[Rupes]

So could you sell these as a standalone product? Sounds like a good business opportunity for one of the e9x vendors.

[Sean1933]

No worries Acree, I'm just an M owner who is particularly tight with his money

Originally Posted by Beemdog

I believe the OP mentioned that it is possible the excess backlash in the worn gear teeth causes the actuator to constantly "hunt" for position when set in that spot. This could lead to the overheating of the motor driver FETs.

This is the thinking as the actuator doesn't have its own optical position sensor so works based on the TPS at the end of each bank, meaning the feedback can cause constant adjustment by the actuator motor. I haven't fully studied the circuit layout but note that the blown Fet is right by the motor connector pins (negative in particular) which would make sense with overheating following constant on/off regulation.

Originally Posted by Rupes

So could you sell these as a standalone product? Sounds like a good business opportunity for one of the e9x vendors.

It's a possibility but the gears are currently high priced as the materials are expensive and custom made to order - I'm looking into the logistics of a bigger batch though

[M33too]

read a couple threads where alpina527 had some custom gears made...

anyone have his contact info or know where to get some upgraded gears?

oddly enough I got engine codes for throttle actuators for about a month straight but has completely gone away for awhile now after resetting.

[dmppdx]

Why was this thread moved into the "M3 vs...." category?

[aussiem3]

I have got the following at least three times in the last couple of months when I have started the car:

• Reduced engine power
• DSC failure
• Flat tyre monitor failure

But if I turn off the car and restart all error messages disappear, and it's fine and car is normal. It's not like I have tried to drive the car with the errors.

Finally I managed to download the error coding when it happened today and this is what I had:

• 2B21 - Throttle valve actuator predrive check bank 1
• 2B57 - Motor emergency program activated

Don't know whether my TVA are on the way out or whether it's an electrical issue.

Anyone wants to shed some light on this please?

Thanks in advance

[Flea7]

Originally Posted by aussiem3

I have got the following at least three times in the last couple of months when I have started the car:

• Reduced engine power
• DSC failure
• Flat tyre monitor failure

But if I turn off the car and restart all error messages disappear, and it's fine and car is normal. It's not like I have tried to drive the car with the errors.

Finally I managed to download the error coding when it happened today and this is what I had:

• 2B21 - Throttle valve actuator predrive check bank 1
• 2B57 - Motor emergency program activated

Don't know whether my TVA are on the way out or whether it's an electrical issue.

Anyone wants to shed some light on this please?

Thanks in advance

yup!
"reduce power"
"DSC failure"
are the two i got along with increased emission, park assist errors as well as the 2B21 error code.

You have the symptoms of a failing TVA.

[aussiem3]

Originally Posted by Flea7

yup!
"reduce power"
"DSC failure"
are the two i got along with increased emission, park assist errors as well as the 2B21 error code.

You have the symptoms of a failing TVA.

Thanks ... I don't know whether Sean's fix will work for this. If not it's going to be an expensive DIY given the stealer price for the parts.

[Sean1933]

Originally Posted by aussiem3

Thanks ... I don't know whether Sean's fix will work for this. If not it's going to be an expensive DIY given the stealer price for the parts.

Hopefully yours is just a gear failure, they seem to go first, then the electrics. You will nearly always have to replace the gears but I'm not sure who can supply them where you are.

You will need to dissassemble and look at the gears then go from there. Given that it is still intermittent it would suggest just the gears at the moment. One thing you can do if funds are really tight is to rotate the middle white gear by 180deg so it uses a less worn contact point on that gear. Although it is unlikely to last long as the black gear is the main issue, and that can't be rotated.

[Sean1933]

Originally Posted by dmppdx

Why was this thread moved into the "M3 vs...." category?

Who knows!

Does anyone know how to contact a moderator to have this moved back to where it should be?

[aussiem3]

Originally Posted by Sean1933

Hopefully yours is just a gear failure, they seem to go first, then the electrics. You will nearly always have to replace the gears but I'm not sure who can supply them where you are.

You will need to dissassemble and look at the gears then go from there. Given that it is still intermittent it would suggest just the gears at the moment. One thing you can do if funds are really tight is to rotate the middle white gear by 180deg so it uses a less worn contact point on that gear. Although it is unlikely to last long as the black gear is the main issue, and that can't be rotated.

Thanks Sean. Where did you get your gears from? I am happy to pay for the postage, and it will be still cheaper given the stealer prices in Australia. BMW parts are like gold here.

[Sean1933]

Originally Posted by aussiem3

Thanks Sean. Where did you get your gears from? I am happy to pay for the postage, and it will be still cheaper given the stealer prices in Australia. BMW parts are like gold here.

They have to be custom made - I am still waiting for mine to turn up, was expecting them before Christmas but not materialised yet. When they arrive I'll test them and if product looks good will pass out his details. ;-)

[aussiem3]

Originally Posted by Sean1933

They have to be custom made - I am still waiting for mine to turn up, was expecting them before Christmas but not materialised yet. When they arrive I'll test them and if product looks good will pass out his details. ;-)

Thanks heaps. Have a Happy and a Prosperous New Year!

[nusevad]

great thread, subed.

[thekurgan]

Damn, some skills in this thread! I'll definitely post pics of my actuators when I take them apart this weekend after I replace with new units.

[alpina-527]

Originally Posted by binh513

read a couple threads where alpina527 had some custom gears made...

anyone have his contact info or know where to get some upgraded gears?

oddly enough I got engine codes for throttle actuators for about a month straight but has completely gone away for awhile now after resetting.

That small reduction gear carries a very high torque loading to open the 8 throttles (10 on S85)

It's hard to see the wear in this pic but it's mainly one 3 or 4 teeth and transfers the wear pattern onto the output gear

It certainly appears that once the gears start snagging, the electrics suffer which results in the burnt Mosfet