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Discussion Starter #1
Been reading about the actuator issues for years. I finally got the P154E code, along with the ubiquitous DSC, Engine, Start Malfunctions, etc...
I've been going back through most of the threads here, and now I'm more confused. Can someone explain some of these things? -
1) What is the difference between an Idle Actuator and a Throttle Actuator?
2) Does the P154E point to a specific bank? I'd like to do both in due time, but I'd like to diagnose this particular fault specifically.
3) I haven't got to pulling the plenums off yet or torn the actuators apart yet, but it seems like many of the issues are from worn gears. After looking around, I see some of the rebuild kits come with brass gears or all plastic. Is there an actual benefit of one over the other?
Seems to be about $50 for the brass - New Throttle Body Actuator Repair Kit Brass Gear & Shaft For BMW 06 - 10 M5 E61 | eBay
$40 for all plastic - For BMW M3 M5 M6 E90 E90 E92 E93 Throttle Actuator Gear Repair Kit | eBay
4) If it's not just worn gears, how do you tell if you have bad mosfets, or a board, in general? Visual? Or, just by ISTA?

Experimenting with this issue, this is what I've found so far -
In a quiet garage, with engine off, I can hear a bit of squeaking when I push the pedal down. I have every intention of lubing the linkage when I get to it, but -
after clearing the codes, the only time I can get the fault to initiate, is at full throttle at highway speeds and at the shift. The reason this is interesting, is I can drive around at city speeds shifting from 6-7th at full throttle hundreds of times without tripping the fault.
 

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It is usually bad electronics that result in the error. The gears wear, which increases play. The electronics then have to work harder to keep the actuators at the desired position, which in turn damages the electronics.

The best and most economical option is to have them rebuild (rebuild.co.uk for example). They will fix and upgrade your electronics, put upgraded gears in, and you'll get a lifetime warranty for around $300 per actuator.

Thats how I fixed them on my car, no issues since.
 

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Literally just dealt with this issue, and it turned to murder. I've had the plenums off 5 times this spring between the throttle actuators, thermostat and vanos solenoids. Anyways, you're asking about actuators. First time I pulled them I replaced the worn gears (mine looked just like all the pictures out there, 06 w/ 100k) with the odometer gears version from FCP. Threw everything back together, same errors, bank 2. Ordered the mosfets off of Amazon and waited a couple weeks for them to come in, pulled the actuators a second time. Bank two actuator only I unsoldered all old mosfets and put new units on, threw everything back together.

Same errors.

Bought brand-new VDO units from FCP w/ lifetime warranty, I was sick of spending 4 hours over and over again trying to not bite the bullet on new units (planned to do the transmission this spring, car had complete other thoughts on the subject). Some have luck swap the gears and drive happily forth, if you want to test your luck I have brand new Odometer Gears already installed on the output shaft (I used a drill press and pinned the gear to the shaft too, no ghetto "JB Weld it on" like the instructions mentioned) and one faultless original actuator that's likely good for the long-haul now. I have no need to store it since the new units are warrantied. PM me if you want to make an offer on any of the parts, I can show receipts displaying how recently this stuff was purchased.

If you have ISTA or something that reads the full codes for BMW it will point to specific cylinder bank. Plenty of good instructions on this forum for how to get to the little buggers. And while you have it all apart, definitely buy the dry white lithium grease and clean out/free up the throttle linkages. They can get grimy over time and some level of thought out there concludes that the increased resistance from turning grimy linkages can help ruin the actuators over time as well.

Get wrenching.
 

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Oh and answer for #1. The idle actuators sit further back in the v, behind the throttle actuators and control the engine at idle. There's two, similar to throttle actuators, one controlling each cylinder bank. The throttle actuators are like big RC Car servos that pull and push on a linkage, connected to a spring-loaded rod that ties together all butterflies for each throttle body on a bank of cylinders.
 

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OP - Save yourself a bunch of future stress.
Rebuilds usually fail within a couple thousand miles, often much less.
Don't take my word for it. Search the forum.
Do it properly and get new TA's.
You absolutely will have to do it sooner or later, and no telling where you will be next time they fail.
Rebuilt TAs only kick the can down the road.
And to this point, I went the rebuild route once out of necessity (via a very reputable M shop) as I was stranded out of town on a holiday weekend and had no other choice.
Failed at around 900 miles.
 

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It is usually bad electronics that result in the error. The gears wear, which increases play. The electronics then have to work harder to keep the actuators at the desired position, which in turn damages the electronics.

The best and most economical option is to have them rebuild (rebuild.co.uk for example). They will fix and upgrade your electronics, put upgraded gears in, and you'll get a lifetime warranty for around $300 per actuator.

Thats how I fixed them on my car, no issues since.
This is the best option for all ///M Owners. These units are an upgraded version of the cheap OEM units. Do not waste your money to buy even new OEM units. Most of us wouldn’t buy OEM bearings. We would always choose an alternative to that. Why? The OEM ones have a faulty design.

Similarly, the OEM actuators are extremely inferior. With plastic gears that chip away day by day. The electronics are not graded for high temperature settings. They also start to fry away.

Rebuild UK or ///M Power Motorsports (North American supplier for Rebuild UK) have come with an improved design by not only replacing the gears with Nylon gears mixed with Carbon Fiber, but the entire electronic makeup of the unit is upgraded. These units are an upgraded version of the OEM units at the fraction of the price. And they come with a transferable lifetime warranty. So it’s a no brainer at the end of the day.


Sent from my iPhone using Tapatalk
 

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I'll clarify my earlier statement... "rebuild kits" usually fail.
I do not have experience with net-new upgraded units.
 

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No one has yet to mention if the gears are the ones that are failing after people replace them, or if its the actual mosfets that continue to burn up regardless if it has new gears, or not?

if Mosfets still burn with gears still in good condition, then its likely because the mosfets were on the brink of failure internally already due to the heat, cycling, age, etc.

if one mosfet burns, i would replace them all.
 

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This is the best option for all ///M Owners. These units are an upgraded version of the cheap OEM units. Do not waste your money to buy even new OEM units. Most of us wouldn’t buy OEM bearings. We would always choose an alternative to that. Why? The OEM ones have a faulty design.

Similarly, the OEM actuators are extremely inferior. With plastic gears that chip away day by day. The electronics are not graded for high temperature settings. They also start to fry away.

Rebuild UK or ///M Power Motorsports (North American supplier for Rebuild UK) have come with an improved design by not only replacing the gears with Nylon gears mixed with Carbon Fiber, but the entire electronic makeup of the unit is upgraded. These units are an upgraded version of the OEM units at the fraction of the price. And they come with a transferable lifetime warranty. So it’s a no brainer at the end of the day.


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any idea what they change in them? Beefed up mosfets with higher amp ratings?

sure would be interesting to see if the mosfets can be stacked so that they handle double the power and take More abuse... or simply add a big heatsink on top of them by using a thermal pad and then a thick plate of aluminum or copper as the heatsink. First instinct would be to use the metal actuator case as the heatsink transfer but i would rather keep it separated due to engine heat
 

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Discussion Starter #11
Finally got around to pulling the actuators out.

For the people in the know, what does the "return" feel like on a good one? It's blatantly obvious one slaps back, whereas the other closes softly.

Other interesting finds - my car is an 06. One actuator is labeled 2008, and the other 2014. Looks like this will be at least my 5th actuator on my car.

Without too much more teardown, is there anything else I should replace with the plenums off?
 

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Finally got around to pulling the actuators out.

For the people in the know, what does the "return" feel like on a good one? It's blatantly obvious one slaps back, whereas the other closes softly.

Other interesting finds - my car is an 06. One actuator is labeled 2008, and the other 2014. Looks like this will be at least my 5th actuator on my car.

Without too much more teardown, is there anything else I should replace with the plenums off?
You asked?? Check the dates on those idle actuators and check the big hoses for cracks - they are not cheap. They might need to get replaced. Also those evap valves and hoses behind them. My E60 is still down cuz I'm being held up by FCP Euro's Economy shipping - BIG mistake I made but that's another story. Also waiting on MPowersports rebuilt throttle actuators. Got a pair but one of them was making a funny noise. They were nice enough to acknowledge the problem and sent me another one as I sent the defective one back. PROBLEM IS, USPS is having what appears to be a problem at their distribution in Michigan - my damn package has been stuck there for 4 days! My E60 has been down for over 2 weeks!
 

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Discussion Starter #13
Update:
Picked up a 2018 version of the actuator from a working pull. It was about $200. What I noticed is that it had the "slap back", instead of the "soft close" while manually working the actuator arm.
Disassembly shows that the 2008 actuator, when putting anything conductive between the 2 pins, would force it to soft close. Pull the conductivity from the 2 pins, and it slaps back. So, without knowing how that works exactly, it at least shows that what they are supposed to do, is slap back. Both the 2008 and 2014 gears looked fine - No excessive wear on any gear was noted.
Installed, and I've put maybe 200 miles on it so far, and car is as good as new. No codes, runs strong.
 
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