BMW M5 Forum and M6 Forums banner

1 - 20 of 56 Posts

·
Registered
Joined
·
164 Posts
Discussion Starter #1 (Edited)
So it's my turn to experience a throttle actuator failure. My M5 is a March 2006 build SMG car with 94,xxx miles, based on the date stamps on the actuators themselves, these are the original units that came from the factory. Seeing as how these are obscenely expensive for what they are (read: poorly designed POS's), I thought now would be a good opportunity to try some of the fixes outlined by fellow board members. Unfortunately, so far I haven't found a fix and I'm looking for some feedback.

My failing actuator only caused my car to go into Limp mode after a restart, once the engine was warm. If I cleared the codes and waited for the engine to cool down, the car started and drove fine.


Post Intake Manifold Removal:
I examined the throttle linkages and opened and closed the valves by hand, I found that my car had the typical squeak other members had reported. Both banks had significant resistance when opening by hand. Part way through their travel you could feel them hang up due to dirt/lack of grease. I took the time to lubricate all of the throttle bodies to help relieve some of the stress on the actuator motors and gear assemblies. They actuate much smoother now, no more hang ups while moving. Moving forward I'd opt to re-lubricate these anytime the intake manifolds are removed.



Video:
Untitled by Jonathan Santarsiero, on Flickr

Pre Tear Down:



Examining the gears:

I expected there to be significant wear considering these are original to the car. What I found was next to no wear on the white center gear, and the typical tooth thinning on the half moon spring loaded gear. I forgot to snap a pic of the reduction gear, but there was very little wear to be seen.

Lots of dust I assume from the gear wear...






The Electronics:

I found some slight discoloration on one of the MOSFETs on the failing actuator. So I opted to try and swap that out seeing as how a few members on M3post had reported success doing so. Unfortunately, this did absolutely nothing. The slight discoloration seen appears to be from the coating applied to the board at the factory, not from a failed component.












Next, I'm considering having the DC motor rebuilt, but my gut says this is another failed component on the board. Any idea what component(s) would work fine when cold and then fail when hot? I still haven't replaced the gears but I'm not convinced new gears would remedy it at this point.
 

·
Registered
Joined
·
5,663 Posts
Typically if the MOSFET goes, the circuit which drives the gate lead on the MOSFET becomes damaged as well. None of the motors I've seen were damaged beyond use, including brush wear. There is a decent amount of carbon dust built up (due to the enclosed can) which alters insulation resistance, but not to the point of reducing motor torque or increasing the current ramp integral the control board reports on.

Ridiculous design. No circuit protection for the most likely means of failure, just a monitoring routine to say it happened.
 

·
Registered
Joined
·
1,724 Posts
That MOSFET was not damaged. The 'discoloration' was simply bunched up & aged conformal coating on the PCB.

Maybe I should get back to this topic some day and finish my job. I am so close to understanding it.
 

·
Registered
Joined
·
1,432 Posts
I have two of these circuit boards from TAs that I recently replaced. With one of them, when I push the little lever to activate the gears etc, it moves fine in one direction but drifts back to rest - like a short in a single direction - maybe something involving a diode(??) The other one is better but fails one of the ISTA tests (the 2nd attempt only). That's enough to make it persona non grata with the car software.
 

·
Registered
Joined
·
5,663 Posts
I have the VDO actuators for $625. I can't keep them in stock, but have an order in with two coming this week.

I hate plugging them here, but it's the cheapest I can source them anywhere and still working on a better design.
 

·
Registered
Joined
·
1,432 Posts
My 2nd actuator just went out on me last night.... :( Does BMW put this **** on a timer or what? tired of paying their insane prices for a dumb actuator. Does anyone have a better source for replacements?
Try fastattackmotorsports.com (JColley) or spareto.com if your credit card or paypal can do foreign currencies.
 

·
Registered
Joined
·
164 Posts
Discussion Starter #9 (Edited)
I have the VDO actuators for $625. I can't keep them in stock, but have an order in with two coming this week.

I hate plugging them here, but it's the cheapest I can source them anywhere and still working on a better design.
Jim, please let me know once you get them assuming they aren't spoken for. I'm getting sick of seeing this car sit and might be interested in taking one of them off your hands.

In the meantime, I'm going to try and remove my bad actuator and have another look at that board. Considering how cheap the majority of these components are, I may just continue to swap questionable pieces out until we narrow down a culprit.
 

·
Registered
Joined
·
164 Posts
Discussion Starter #10
No real updates yet. I just placed an order with Jim's company to get a brand new actuator so I can actually drive the car occasionally.

I may try and bake the electronics from the bad actuator like others have tried with a failing graphics card from a computer. The heat should help reflow the solder joints. Figure it's a $600 paper weight to me now, so I can't really make it any worse.

Additionally, my car now enters limp mode immediately after a cold or warm start. Strange that it would go from being somewhat temperature dependent to just completely not working now.
 

·
Registered
Joined
·
164 Posts
Discussion Starter #11 (Edited)
More bad news to report, I baked the bad board from my failed actuator but it didn't remedy the issue. I knew it was a long shot but it was free to try, so I had nothing to lose. Unfortunately, my car is now failing pre drive checks for both banks. Is it possible one of these codes is being thrown simply because of the one bad actuator? I swapped them side to side with no change, I also unplugged them one by one and read the subsequent codes to ensure it wasn't a connection issue.



I have one new throttle actuator set to arrive on Tuesday, I'm praying I only have one that's failed and the code for the other is sympathetic to the failed one.
 

·
Registered
Joined
·
1,724 Posts
Noop. They usually go in pairs or shortly after one another. What are the NEW codes? Clear them first to be sure.
 

·
Registered
Joined
·
164 Posts
Discussion Starter #13
Noop. They usually go in pairs or shortly after one another. What are the NEW codes? Clear them first to be sure.
Figures they go in pairs. I've cleared the codes multiple times after swapping the actuators bank to bank, but I'm still getting both actuator codes. Not sure offhand which ones specifcally, but I'll report back.
 

·
Registered
Joined
·
1,724 Posts
Not always. But they wear at the same rate. So it is very likely. Consider yourself lucky. Swap it all at once instead of doing it all over him in a few weeks. Of course it cost a bit. But this car ain't cheap to maintain.
 

·
Registered
Joined
·
164 Posts
Discussion Starter #15 (Edited)
Just received my new actuator, plugged it in and now I only have one bank failing a pre start check again. Looks like I'll be ordering another new actuator to match.

The codes I've been getting are:
-2B21 Throttle Valve Actuator Pre-Drive Check Bank 1
-2B22 Throttle Valve Actuator Pre-Drive Check Bank 2
-2B57 Motor Emergency Program

The DSC module also threw a code related to the Limp Mode. But I'm assuming that will become clearable once both banks pass their pre-drive checks.

Oh and the throttle actuator test in INPA is pretty much worthless. Watching the new actuator go through it's full range of motion was pretty neat, but the failed actuator doesn't budge. And INPA just says "System load complete run through and error recognized". No sh!t sherlock. Hahaha
 

·
Registered
Joined
·
1,724 Posts
You get a DSC error because the TA are part of the brake vacuum assist in case the vacuum assist pump fails. The DME can shut down a whole bank and close the TA to turn it into a giant vacuum pump to ensure your brake power persists. Yes, when your TA are health this DSC error goes away.
 

·
Registered
Joined
·
164 Posts
Discussion Starter #17
You get a DSC error because the TA are part of the brake vacuum assist in case the vacuum assist pump fails. The DME can shut down a whole bank and close the TA to turn it into a giant vacuum pump to ensure your brake power persists. Yes, when your TA are health this DSC error goes away.
Makes sense, thanks for the explanation.

Has anyone had issues with their TA's due to low voltage? Because my car has been sitting for a few months now, I just got a low battery voltage warning on the cluster. And ever since then my one good working actuator is failing it's pre drive check. Has anyone tried swapping out the voltage regulators on the TA board?

I charged the battery overnight so I'm going to try again today and see if I can coax some life into that actuator.
 

·
Registered
Joined
·
1,724 Posts
Likely not. There are two voltage regulators. One for the logic which is a 5V regulator with a reset. And a separate one (for redundancy) for the throttle position sensor. Everything else is battery referenced. I believe the TA stops working below 8V. Your car won't crank at 8V anyways. The micro is still working at that point, but it refuses to control the H bridge below that voltage. Aside from this there is ground referenced main switch that shuts off the H bridge all together.
 

·
Registered
Joined
·
164 Posts
Discussion Starter #20
Likely not. There are two voltage regulators. One for the logic which is a 5V regulator with a reset. And a separate one (for redundancy) for the throttle position sensor. Everything else is battery referenced. I believe the TA stops working below 8V. Your car won't crank at 8V anyways. The micro is still working at that point, but it refuses to control the H bridge below that voltage. Aside from this there is ground referenced main switch that shuts off the H bridge all together.
Sounds like my voltage regulator is fine. My battery was only down to 11.5 volts when it threw the 2nd failed actuator code.
 
1 - 20 of 56 Posts
About this Discussion
55 Replies
18 Participants
hoodust
BMW M5 Forum and M6 Forums
M5Board is the best forum community for information on the BMW M5 E60 (V-10), E39 (V-8), E34 (straight 6), E28, F90 and F10. Discuss performance, specs, reviews and more!
Full Forum Listing
Top