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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 Thu, Jul-19-2012, 04:00:38 AM   #1
RotRot
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Default DIY: The "Standup" SMG Resistor Mod

OK, believers in small fixes, here's my story.

Shortly after my 2003 M3 'vert came out of CPO warranty, I started
having the high-temp SMG-II disengagement blues. I did a lot of
on-line research, but at the time there were many more theories
about the cause of the problem than reported solutions.

To keep this short, I'll simply say that over the course of many
months, I replaced the salmon relay, got a new accumulator installed,
and put in a new SMG temperature switch (#13 62 1 433 076). The
switch seemed to cure things for a while, but ultimately the issue
returned.

So yesterday I did the resistor fix -- the one proposed here
http://www.m3forum.net/m3forum/showp...&postcount=191
by 'SteveEvans,' using a 1/2 Watt carbon resistor in the under-hood
electronics bay instead of a 10 Watt wirewound down near the driver's
side front wheelwell. This method does not require jacking up the car,
crawling underneath, or 25 minutes of hand-washing after you're done.

With the usual disclaimers about not being responsible for permanent,
irreversible, and extremely costly damage due to properly or
improperly following the steps outlined below, here is the rundown:



Stuff I bought at Radio Shack: Package of 1 KOhm, 1/2 Watt carbon
resistors ($1.19), Five-Piece Soldering kit -- which includes a 30 Watt
soldering iron and enough resin-core solder to handle this job and
more ($9.99), Package of assorted heat-shrink tubing ($4.19).
Total $15.37 + tax.



Tools I had: Screwdriver with PH2 Phillips and T25 Torx bits, small
diagonal wire cutter, and wire stripper. (Not pictured: butane
cigarette lighter or just plain matches for the heat-shrink.)



The worksite: The M3's electronics bay is under the hood, to the
rear, on the driver's side. It is an enclosed box with a
plastic lid secured by three somewhat shiny Torx screws and one
black colored Phillips screw. All four screws should be completely
removed. The cover willl swing upward about 30 degrees on its
near-side hinges; then you can pull it away from the hinges for
removal. This requires a little bit of force, but I didn't see
anything that's likely to break.



Inside the bay, there are several wire bundles terminated by
gray connectors. We're interested in the bundle that's just
above and a little to the left of the blue relay.



Here is the wire group we want. Un-plug the connector by
pressing a small button that frees the black retaining lever,
then rotating the black lever downward.

...to be continued....

Last edited by RotRot; Sun, Jul-22-2012 at 12:20:29 AM. Reason: Use photobucket pictures.
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Old Thu, Jul-19-2012, 04:07:53 AM   #2
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Default Re: DIY: The "Standup" SMG Resistor Mod

...continued from above....



This is the wire bundle removed from its socket. In the photo,
close to the connector, there is a white wire inbetween the
green and brown ones. That is the target. To double-check,
you can look on the mating surface of the connector and verify
that the white wire is going into hole #21.



Now the white wire we're going to cut needs to be isolated from
the rest of the bundle so that we can work on it. Remove the
cloth wraparound nearest the connector, then pull the wires apart
until the white wire can be arced one way and the rest of the
wires pushed in the other direction.



Point of no return. The white wire has been cut and stripped.



I also like to "tin" the stranded wire before wrapping it to
the resistor leads and making the final solder joints. Note the
heat-shrink tubing put in place before attaching the resistor.



At this point, I have soldered to the resistor on both ends, cut
off all excess leads protruding from the solder joints, pulled the
heat-shrink over the connection, and used a butane cigarette
lighter to shrink down the tubing.

...to be continued....

Last edited by RotRot; Sun, Jul-22-2012 at 12:31:38 AM.
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Old Thu, Jul-19-2012, 04:12:46 AM   #3
RotRot
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Default Re: DIY: The "Standup" SMG Resistor Mod

...continued from above....



And here, the wire bundle has been re-assembled, the cloth wrap
put back in place, and the connector re-mounted. Start-to-
finish, the job took less than an hour -- including some
interruptions to talk to a neighbor, answer a couple of phone
calls, and find the butane lighter.



Now it's time for another 94,000 miles of RotRot driving!


NOTES

Some choices I made and why:
-- I used a 1K resistor instead of the 3K value recommended
elsewhere because I was hoping to retain some amount of over-heat
protection in the circuit. At some point, I may even drop my
1K down to 500 Ohms.
-- I used clear plastic heat-shrink tubing even though white
was available and might look more "professional." I decided
that I wanted anyone working on the car, or any future owner,
to be aware of the modification and able to determine the
resistor value.

Acknowledgement and many thanks should go to several people who
have gone where BMW refused to go: to the apparent root cause
of the highly dangerous and value-slashing failure of the SMG-II
transmission system. As far as I can determine, the first
person to propose a resistor bias on the heat sensor circuit
was '03DinanS2' on another forum. Closer to home, 'cntrvrsy'
did yeoman's work with his write-up on what I call the
"Underneath Mod" -- spawning a thread that has gone to more
than 200 messages. And more recently, 'SteveEvans' suggested
the "Standup Mod" that produced this post. Kudos, gentlemen.

Last edited by RotRot; Sun, Jul-22-2012 at 12:24:38 AM. Reason: Use photobucket picture(s).
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Old Thu, Jul-19-2012, 05:23:48 AM   #4
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Default

Nais! Keep us updated
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Old Thu, Jul-19-2012, 05:30:40 AM   #5
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Default Re: DIY: The "Standup" SMG Resistor Mod

Just a couple of more items:

What led me to doing the above mod was the recent series of New Jersey heatwaves. My tranny was embarrassing me and putting me, and others on the road, in danger.
In two days since the resistor install, with ambient temps in the high 90's, I have intentionally strained the SMG every way I know how -- and I've yet to see a trouble light, much less drop out of gear.
I plan to update this particular message on a routine basis so you can follow the success, or lack thereof, for the mod.

I'd also like to name some winners and sinners in my history with the SMG problem.

When I bought my car, it was under CPO warranty from Peter Pan Motors in San Mateo, CA. I had a continuing series of complaints about transmission issues, including shudder during auto-downshift, gearbox warning lights, and a single failure-to-engage. The Peter Pan folks had a continuing series of "unable to duplicate" and "no diagnostic fault indicated" responses. Every time I would ask for written documentation of the diagnostic tests performed and their results, and I would be told these were not available.(Additionally, when I took my M3 for a Service II at Peter Pan, I asked for documentation from the valve-clearance check and I was told, "We don't do that" -- meaning they didn't do the check or shim adjustments at all. Not because it was under warranty, do you suppose?)

On a decidedly more positive note, I've had a few occasions to deal with Paul Miller BMW in Wayne, NJ -- and specifically a Service Rep named Ken Walters. He has gone out of his way to listen to my concerns and try to address them. With the SMG issue, he had nothing better to offer than the "pump unit replacement" solution -- because that was the BMW party line. But, given my documented history of tranny complaints (even though they were to an unrelated dealership 3,000 miles away), he offered to get the job done "at cost," meaning his dealership would make no profit on the parts or labor. This would bring the cost down from approx $5,200 to $2,600. (Some day, when all else has failed, I may regret my decision not to go this route.)

Back on the negative: BMW North America was not just useless, but insulting. The rep I talked with on the phone listened to my history in-warranty SMG complaints to Peter Pan, and my conclusion that the dealership had failed to make a proper diagnosis. His conclusion was, "Warranties have an expiration date. Yours has expired. There's nothing I can do for you."

Now the best: Since coming out of warranty, I have dealt almost exclusively with Motor Works West in Wycoff, NJ. My car and I split our time between California and New Jersey (yes I drive both ways, mostly with NAV set to 'avoid highways'), and I try to time all my maintenance so that MWW gets the job. One of their techs, named Sean, is amazingly smart on the SMG system, and he has done everything possible to keep me away from a dreaded pump-unit replacement. The main guy at MWW, Steve, is a car dude through and through and will even talk to me about my mistress, a '67 Alfa Duetto, when my wife, the M3, is in his shop for service. If you can get to this place -- even from California -- I couldn't recommend it more.

Disclosure: no personal, non-customer ties to any entity above.

Last edited by RotRot; Tue, Jul-24-2012 at 06:31:03 AM. Reason: gramma
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Old Fri, Mar-06-2015, 12:21:50 AM   #6
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Default Re: DIY: The "Standup" SMG Resistor Mod

Thanks for doing this DIY.
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Old Fri, Mar-13-2015, 05:51:45 AM   #7
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Unhappy Re: DIY: The "Standup" SMG Resistor Mod

I just finished this mod, much better than getting under the car. As mentioned amongst all posts regarding this subject, if my pump was going bad, then there's nothing to lose anyways. I got all the same parts mentioned from radio shack.

I can't wait to see if it helps out. Parking on the side of the road in traffic to cool down sucks arse.
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Old Fri, Jul-10-2015, 11:31:57 PM   #8
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Default Re: DIY: The "Standup" SMG Resistor Mod

I can attest that this modification works! I just moved to Hawaii with 90-94 degree heat and some of the worst traffic in the United States.

The orange SMG light, P1717 code, and P0700 code would be triggered frequently even with the A/C off. I could not drive very far or long before the light would go off with temperatures above 80 degrees. However, it was completely fine at night with no A/C. I changed the salmon relay and topped off the Pentosin CHF 11S fluid (it was really low), which did not resolve the problem.

I used a 3.3k ohm resistor just in case. It's been three days. I drove through stop and go traffic jams during high noon with the A/C on full blast. I've been monitoring the ranges of the oil temp (~210 F max); coolant temp (~198 F max w/ Water Wetter and 80/20 coolant and distilled water ratio); and air intake temp (~130 F max) during traffic jams in direct sunlight. Not a single hiccup.

O'Reilly's had the parts for half the cost of RadioShack with exception to the resistor. This mod saved me the diagnostic fee and the cost of a new pump that might not have solved the problem. I thought about buying a daily driver for really hot days, but luckily I don't have to worry about that anymore! Thank you!
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Old Fri, Jul-10-2015, 11:45:54 PM   #9
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Default DIY: The "Standup" SMG Resistor Mod

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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Last edited by WOLFN8TR; Sat, Jul-11-2015 at 12:41:22 AM.
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Old Sat, Jul-11-2015, 10:07:50 AM   #10
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Default Re: DIY: The "Standup" SMG Resistor Mod

Excellent DIY. Thanks.
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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)