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Faults, Fixes and DIY Please share your experience and knowledge with other members by contributing your own DIY, or by helping another member find the elusive fix!


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Old Sat, Jul-08-2017, 02:54:26 PM   #71
RGT74
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Default Re: DIY: The "Standup" SMG Resistor Mod

I've been having this issue intermittently with temps in the 80-90 range. I just did this mod with the 680 1/2W resistor. Went to track yesterday for a true test and ran 66 laps with temps up to 99deg by afternoon. Cog light did not come on and SMG performed without any issues. My issue now is coolant temp getting up to the red zone on gage! But that's for anothe thread.

Thank you all. I don't post much, but I use this forum a lot. I've had my M3 for 3+ yrs now and I've experienced many of the issues discussed here. I've fixed many things with DIYs like this one. Great work!
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Old Sun, Jul-23-2017, 10:02:12 PM   #72
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Default Re: DIY: The "Standup" SMG Resistor Mod

Did this mod yesterday with a 1k ohm, 1/4 watt resistor. Working well, will report back in a few months
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Old Tue, Aug-08-2017, 05:22:49 PM   #73
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Default Re: DIY: The "Standup" SMG Resistor Mod

Drove around yesterday in 92 degree heat for about an hour. No light. Then started up the car around 3 hours later in 80 degree heat and had the smg cog light showing. I checked for a code and there were no codes. Started up the car again and light was gone. Not sure what's going on, but I'll keep tabs on it.
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Old Fri, Sep-01-2017, 03:40:27 PM   #74
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Default Re: DIY: The "Standup" SMG Resistor Mod

It's my first summer with this car, and I had bookmarked this thread in case of this issue coming up. I figured that living in the PNW I wouldn't ever see temperatures high enough to trip a cog light... I was wrong.

Earlier week on the drive home in stop & go freeway traffic with A/C on, the cog light comes on Dash temperature read 92* although it didn't "feel" in the nineties. My commute on the way home is 1.5 - 2hrs so I was pretty nervous. It never dropped out of gear, but I went home and ordered the resistor anyway.

I pulled the codes and it seems consistent with this temperature issue based on this thread:
http://www.m3forum.net/m3forum/showthread.php?t=416689

Last night on the way home, in traffic, full A/C again, I get the cog light. My drive isn't even half over. It ends up dropping out of gear a few times and I pull off the freeway, find some shade and pop the hood. I let it cool down for a while and eventually I am able to limp it home (as it drops out of gear a few more times along the way).

Of course my resistor won't be here for another day (couldn't find anything local) so I won't be driving the car til I do this mod. The summer heat is just about over here but I will keep the thread updated with my findings.
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Old Mon, Mar-05-2018, 01:46:05 PM   #75
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Default Re: DIY: The "Standup" SMG Resistor Mod

Does anyone have the photos from the first page that they can repost.
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Old Mon, Mar-05-2018, 08:19:12 PM   #76
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Default Re: DIY: The "Standup" SMG Resistor Mod

Quote:
Originally Posted by kingofqueenz View Post
Does anyone have the photos from the first page that they can repost.
Get the photobucket embedded fix and it'll work. I just used this DIY a month ago.
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Old Mon, Mar-05-2018, 11:50:36 PM   #77
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Default DIY: The "Standup" SMG Resistor Mod

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Originally Posted by kingofqueenz View Post
Does anyone have the photos from the first page that they can repost.

I have some of them. Here ya go.












The 3.3K resistor is way to high, 1K was recommended. There's a member on here that tested several of these resistors and found the 680 ohm resistor was the best because it doesn't allow the hydraulic pump pressure to drop too low causing other issues. I will see if I can find his thread.

Steve Evans Post:

SMG hydraulic temperature sensor issue
http://www.m3forum.net/m3forum/showthread.php?t=416689

The value is potentially more of an issue, but exactly how much is hard to say.

With the hydraulic fluid at 59-60 degC and with the sensor reporting normally with no resistor, INPA reported a max accumulator pressure of 75 bar which is what I'd expect.

If you look HERE you'll see that I did an experiment to artificially raise the temperature. At 100 degC the accumulator was primed to in excess of the 80 bar normal limit as shown below where 84 bar was reported.



It is clearly therefore not a good idea to run with a temperature sensor fault which is reporting too high a temperature as it will stress the system. For this reason I chose to limit the temperature to no more than 60 degC. This would require a 596 ohm resistor should the temperature sensor fault short circuit. The next highest (E12) standard resistor I had to hand was 680 ohms so I chose to use that.

This resulted in a reported drop from 59 degC to 37 degC. There was also a corresponding drop from 75 bar max pressure to 69 bar.

At a "normal" operating hydraulic temperature of 70 to 75 degC the ECU should be seeing about 45 deg C with this resistor in circuit. That should see the max hydraulic pressure up in the low to mid 70s bar, more or less where is should be.

When the car is cold I have seen the pressure maxing out in the low 60s. If you use a 1K resistor then at such "normal" operating temperatures the ECU will be seeing something in the mid 30s degC which should give max accumulator pressure in the high 60s bar. With a 3K resistor however the ECU will be seeing approx 10 degC. At this temperature your accumulator will only get pressurised up to the low 60s bar, over 10 bar lower than it really should be.

What's the effect of lower pressure? The pump motor will certainly have to run more frequently, which means more starts, and therefore more wear on the salmon relay and the motor commutator/brushes handling the high start current. As for the effect on the hydraulic system performance I'm not sure; it'll still be within range and should function fine, but you'll not be getting the most out of the system as BMW designed it.
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Old Tue, Mar-13-2018, 06:13:28 AM   #78
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Default Re: DIY: The "Standup" SMG Resistor Mod

Can this be done along side theresistor that's on the bottom? When I bought my m3 the guy said he did the resistor mod but instill got the light and kicked out if gear 3 times and of the times I was on a busty stop and go high way thanks!

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Old Wed, Apr-25-2018, 09:13:04 PM   #79
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Default Re: DIY: The "Standup" SMG Resistor Mod

Just finished this mod yesterday, instead of one 680Ohm I soldered two 330Ohm 1/4W in series, 20Ohm difference isnt much anyways, then installed into the wire mentioned by OP.

Also for those who is worrying about the power rating, rest assure, the maximum voltage supply on that line is 14V, even if all 14V is applied on the resistor you installed (not gonna happen whatsoever), the maximum power dissipation on it will be 14^2 / 680 = 0.29W. To ensure the resistor dosent get toasted, if you only got 1/4W ones, split into two (use two 330Ohm as example), that way the max power dissipation on each will be only 7^2/330 = 0.15W
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Old Thu, May-03-2018, 06:34:50 PM   #80
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Default Re: DIY: The "Standup" SMG Resistor Mod

After doing this my car did go over half on the oil temp and no light came on

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Discussing DIY: The "Standup" SMG Resistor Mod in the Faults, Fixes and DIY Forum - Please share your experience and knowledge with other members by contributing your own DIY, or by helping another member find the elusive fix! at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)