Another Throttle Actuator Failure/Tear Down/Attempted Repair - Page 3 - BMW M5 Forum and M6 Forums
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post #21 of 55 Old 16th August 2016, 01:28 AM Thread Starter
Niart906
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So I made another attempt at repairing one of my failed throttle actuators today. This time I swapped out all 5 MOSFETs as well as a 2200uf capacitor hidden on the back of the board. Unfortunately it's still failing the pre drive check. I have a few more components that I will try and swap out tomorrow, but I'm running out of easy components to swap.








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post #22 of 55 Old 16th August 2016, 01:32 AM
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https://www.m5board.com/vbulletin/e60...rmation-2.html

The TA decides itself to go out for lunch. See my latest experiment. The electronics are not broken. I got @gmak 's broken unit and it worked on my bench just fine.
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post #23 of 55 Old 16th August 2016, 01:32 AM
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Originally Posted by Niart906 View Post
Sounds like my voltage regulator is fine. My battery was only down to 11.5 volts when it threw the 2nd failed actuator code.
The TA works below 7V, almost down to 6V.
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post #24 of 55 Old 16th August 2016, 01:46 AM
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https://www.m5board.com/vbulletin/e60...rmation-2.html

The TA decides itself to go out for lunch. See my latest experiment. The electronics are not broken. I got @gmak 's broken unit and it worked on my bench just fine.
Which one? The one with the sharpie writing, or the other one?
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post #25 of 55 Old 16th August 2016, 12:11 PM Thread Starter
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Originally Posted by rt7085 View Post
https://www.m5board.com/vbulletin/e60...rmation-2.html

The TA decides itself to go out for lunch. See my latest experiment. The electronics are not broken. I got @gmak 's broken unit and it worked on my bench just fine.
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The TA works below 7V, almost down to 6V.
Well, as pointless as it seems, I bought a new voltage regulator to try and swap out. For as cheap as they are it's nice to be able to cross components off the list.

Thinking more about your recent experiment, can the DME recognize one TA from the other? Is it possible these are somehow blacklisted from working since they failed pre-drive checks?

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post #26 of 55 Old 16th August 2016, 06:35 PM
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Good thinking.

I am certain that BMW and most auto manufacturers would rather leave you stranded than risk an unintended acceleration lawsuit if the functionality of any part of drive by wire throttle system is in doubt.

Anyone for a stack of Weber Carbs and a mechanical linkage? just need 5-carbs turned sideways
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post #27 of 55 Old 17th August 2016, 04:51 AM
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The TA does report a status byte to the DME but it seems to be the 'decision' of the TA to disable its motor drive bridge. The DME maps the byte value to an error code.

That said, I am wondering if I caused it. The way I control it at the moment is by programming 0%, 10%, 20%, ... 100% steps. These settings are associated with the number keys on my keyboard. To keep it programmatically simple. I am not ramping up and down between the values when I 'play my TA piano'. Since I am very abruptly changing the opening values from one to the other, I am wondering if I introduce a lot of settling error given that I have worn gears in my setup. Could in be tripping it over a certain (integration) value leading the fault logic to trip for safety reasons? I will have to experiment by adding ramping to my code. Easy enuf.

Beyond that I am wondering if I can kick the TA through some kind of re-initialization command. In my data logging efforts I did not find evidence of such a re-initialization. But I logged on 2 freshly replaced TAs pressing the gas pedal. I should have logged a ISTA/D TA test session. I bet it does this cal if it exists. Or in DIS which has a TA initialization command, supposedly.

Another thing I noticed is that the processor on the TA has a UART (TTL level serial port). I sniffed it with my scope. It pulses once when the processor comes out of reset. But it does not 'talk' characters. The pins are left unconnected. However, sometimes you have to wake these ports up by sending a return character or the like in first. I will do that later this week. Need to dig up my USB to 5V UART TTL converter cable. Sprechen Sie Deutscher ASCII?

Last edited by rt7085; 17th August 2016 at 05:53 AM.
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post #28 of 55 Old 17th August 2016, 05:06 AM
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I believe the DME commands the initialization routine on startup. That would seem to mean, it's broadcast over PT-CAN to conduct that.

The DKG adaptation values are reset and relearned under specific circumstances in the DME software. This would all be determined during this self-test phase. Just need to figure out which part of the message commands it.
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post #29 of 55 Old 17th August 2016, 05:20 AM
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Which one? The one with the sharpie writing, or the other one?
The one with the sharpie writing on it. What does that mean?
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post #30 of 55 Old 17th August 2016, 05:47 AM
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I believe the DME commands the initialization routine on startup. That would seem to mean, it's broadcast over PT-CAN to conduct that.

The DKG adaptation values are reset and relearned under specific circumstances in the DME software. This would all be determined during this self-test phase. Just need to figure out which part of the message commands it.
Yes. I have the control message commands fully worked out. In the response, the last byte (7) is still a bit of a mystery. There are only 8 bytes in and 8 bytes out, some of which are simply message sequence counters and checksums which are useless for control other than assuring quality of service of the CAN messages. There is a standby - ready - active status byte. One broadcast message controls both TAs; they get their controls at exactly the same time, albeit that both TA get each their own in separate words. The numbers are always the same. Then both TAs respond in different messages (CAN IDs) affirming what TA opening postion they measure from the position sensor. So, the point is: A possible TA initialization can only be accomplished by sequencing through states in a particular order and/or by setting certain positions (min/max) and comparing the results from the 2 independent position sensors per side: One directly to the DME and one to the TA. And this is of course done for both sides. The latter would mean that the DME is fully handling the adaptations; the TA knows nothing about it. This makes sense. The TA should be 'dumb control plant' with safety belts and suspenders.

Incidentally, I just walked by the TA and decided to flip the power on and run the control software. @gmak 's unit worked again! Then after power cycling it went back out for lunch. (No, I do not have a loose connection.) This leads me to *believe* that this may be a hardware issue after all. Lucky for us, I logged the bus data which it worked and after it stopped responding. So, I have to compare the 2 traces to see where it diverges. Stay tuned. Going to sleep now.

I am taking this back to my DKAN thread..... later.

Last edited by rt7085; 17th August 2016 at 05:57 AM.
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