BMW M3 (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)

BMW M3 (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X) (
-   E46 M3 (2001-2006) (
-   -   SMG troubleshooting FAQ (

m3 hal Wed, Oct-01-2008 05:10:03 PM

SMG troubleshooting FAQ

General SMG system information:

SMG Serviceable Parts

hydraulic unit (aka the pump)
PN: 21532229715
DIY replacement thread:
DIY guide by Mr. Andersen:

accumulator (included with the hydraulic unit but also available seperately)
PN: 21532229716

relay (salmon colored, located in the relay box on top of the drivers side shock tower)
PN: 12631742690

gear position sensor (located near the back of the transmission)
PN: 23412229792

actuators (mechanical arms used to physically change the gears)
PN: 23412229789

hood sensors (two switches located under the hood to detect when open/shut)
PN: 61319119052

SMG hydraulic fluid (Pentosine CHF11s)
PN: 81229407758
My current thinking is that a full hydraulic fluid change would be a tad bit on the expensive size and probably unnecessary. However if you've got a lot of miles you may want to consider using a device to syphon fluid out of the reservoir for a partial fluid change. This way you don't have to worry about properly resealing the system or getting air in the lines.


The Autoenginuity tool is an excellent tool for troubleshooting the SMG system and can take a lot of guess work out of the equation in some cases. Generic code readers are mostly useless since the trouble codes it returns are usually non-specific and the descriptions are typically not accurate. The Autoenginuity also allows for DIY work such as clutch changes and pump changes to be done at home in the proper way.

Specific Issues

--Car won't engage 1st gear or reverse after cranking, drops out of 1st, won't start, weak remote key, or other minor nuissance.

Before getting too worried, open and shut the hood once or twice, and make sure all doors/trunk are shut. If still no luck, replace the relay. In general, whenever there is any type of problem with the SMG that seems electrical related, go ahead and replace the relay first. It seems to be a pretty common problem and can cause a wide range of issues. The part is ~$15-$20, takes 5 minutes to replace, and it's a cheap solution that should be ruled out early when trying to diagnose an issue.

Also check the hydraulic fluid level on top of the intake manifold. I have had the car not want to hold a gear and the transmission light came on simply because it was low on fluid. (note: the SMG system "shouldn't" be consuming/leaking fluid, mine was low from a Delage install were I swapped fluid reservoirs and forgot to refill the new one).

-- 2->3 shifts became "delayed". *Sometimes* when shifting from 2->3 it would take 4-5 seconds to engage the gear and the gear indicator (3) would flash on the dash during this time. I had zero power during this time, and was basically coasting. Eventually it became so bad it wouldn't even go INTO gear and then start skipping gears (2->5 instead of 2->3). (original post:

Replace the gear position sensor.

--No noise from the pump when unlocking the car. Transmission will not engage any gear.

If you've already replaced the relay and there's still no noise from the pump, the hydraulic unit has likely failed.

If the pump makes noise but will not engage a gear, I'm curious as to whether just the accumulator may be the issue, since the hydraulic unit comes w/ the accumulator from the dealer, and the accumulator is also available separately and costs ~$450, it may be the part that wears out. It's an expensive risk to take though, because if the accumulator is not the problem, then it's the cost of labor x2 and you have to rebuy the accumulator when you get the new pump. If it does fix the problem, it would result in about $1k or so in savings. If somewhat had some input on what the accumulator actually does (stores built up pressure?), that would maybe clear this up.

--Red SMG light on and or flashing gear numbers.

Check/replace the hood sensors.

--3rd to 4th shift delay (broken $2 spring):

--Transmission light comes on after car heats up. Car violently jerks in and out of gear, and limps forward. Shows fault code - 0028 - faulty clutch position sensor

Replace clutch slave cylinder.

SMG paddle and paddle switch replacement DIY:

PM me with revisions/input

Leo Thu, Oct-02-2008 05:38:10 PM

Maybe this can answer some of the questions you have?

If something is missing or incorrect just send the maintainer an email. I'm sure will be happy to for the information.


m3 hal Thu, Oct-02-2008 09:17:08 PM


Originally Posted by M3FORM33 (Post 3355711)
Great write up Hal, its gonna be a very usefull piece as people start getting more mileage and start having probs with the SMG. I went through hell and back with mine!

Thanks. If you experienced some problems and got them worked out, and I don't have them in the thread already (or if my descriptions are incorrect or incomplete), send me a pm or post them. :thumbsup2:

Pantera Sat, Oct-18-2008 12:39:09 AM

Intriguing symptom
The timing of this couldn't have been better, although I wish I wouldv'e found it prior to being charged about $350 in diagonostic fees.

Sadly I found the thread regarding the failed relay the same day that the Service Tech figured it out and thus the education from here was free but the cost of repair was significantly higher than necessary.

My contribution to the thread is that there seemed to have been an increasing weakness in my remote being able to open the doors. I initially equated the weakness to a remote battery problem, but it wasn't until after I had the relay replaced that I noted the significant improvement in the performance of the remote. I should note that the weakness increased for at least a week before the relay starting acting up.

The first time the car failed to start I surmissed the problem was battery failure (who hasn't had their BMW OEM battery fail?). I jump started the battery and everything, aside from the door locks, seemed to function fine. The car continued to start multiple times that day, and even the next. Then on Monday morning, wouldn't you know, the car wouldn't start. I put the battery on a newly purchased Sears diagnostic battery charger. The charger indicated the battery was 100%, but I went ahead and put it on rapid charge, 30A, to kick it in the ass. I put the battery back in and the car started. I drove the car directly to the BMW dealer where they did other standard maintenance while diagnosing the (relay) problem.

I don't believe that it was mere coincidence that the remote performance improve dramatically after the relay replacement.

Edit: I noted in other threads about the door lock problems before the relay failure.

I'm definitely going to have a spare relay in each of my M3s.

BTW, my car had about 46k miles on it at the time of failure.

loveM Sun, Oct-19-2008 03:27:59 AM

Unfortunetly, i have an other problem with smg, all the 100 kilometers, the gearbox make a noise (the same that you not take the clutch with a manual gearbox) and the gear get s3 mode at 4000 tr/min between 3 and 4 gear.

The car was 50000 kilometers, no launch control, new gear oil at 27000 kilometers.

Bmw after a check and test, 3 default code , bmw says that the clutch was probably out.

My car was 2004, also no Warranty.

I have tell to him that : ok, my clutch is out, what's the really problem with the little kilometer? Was the same problem than the m5 e60 with the bad Flywheel?

I wait to an other answer from Bmw Germany...

Thank's to your advice...

m3 hal Sun, Oct-19-2008 05:16:36 AM


Originally Posted by Pantera (Post 3393022)

My contribution to the thread is that there seemed to have been an increasing weakness in my remote being able to open the doors....

added a mention of this to the relay troubleshooting

Thanks for the comments everyone. Post your issues/resolutions/part number if you don't see it here.

yaja23 Sun, Oct-19-2008 05:30:51 AM


Originally Posted by drunk hal (Post 3394970)
added a mention of this to the relay troubleshooting

Thanks for the comments everyone. Post your issues/resolutions/part number if you don't see it here.

You might want to add information about checking the SMG fluid to make sure its full and checking for leaks etc. I remember someone posting here about a SMG issue and it was caused by a kink in a hose coming from the SMG reservoir.

Icecreamfoo Sun, Oct-19-2008 07:04:51 AM

my contribution to this thread:

Gear Identification Switch - part # 23412229792 (this is probably the gear position sensor OP listed).

My symptom: yellow SMG warning light. Transmission unable to hold gears and will pop back into neutral (which is fortunate that it doesnt lock in gears and still allows me to restart the car). Able to get into reverse, but passenger rear view mirror won't tilt down, as if the car doesn't realize it is in R. Once the transmission pops into neutral it will no longer engage any gear.

alpina527 Sun, Oct-19-2008 10:12:31 AM

My problem was that I couldn't do a full throttle shift at over 5k revs. The next gear number would flash, and the engine would die until it dropped to 2k. It would then shift up to the next gear and pick up speed again.

It was ok if I lifted off the throttle when I pulled the paddle at up to 7k.

The strange thing was that there were no codes logged. The only indication of a fault was if you went through the software re adaptation stage, when 'shift pattern too large' was logged.

The cure was a new box. This was only found to be the problem after replacing all sensors, hydro pump, actuators and smg software.

alpina527 Sun, Oct-19-2008 05:09:21 PM

One thing to take into account on this type of thread, is that the dealers sometimes throw a new pump or tranny when its something simple like a switch or similar which the customer will never be aware of.

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