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Yellow Cog light showing up but car runs without problem

28K views 31 replies 9 participants last post by  illestminimike 
#1 ·
Hey guys,
I have a 2003 M3 vert with 78,xxx miles. So I went through the whole SMG fiasco where my car stopped in gear shifts and went to neutral (limp mode) and had to wait a couple hours before driving it again in +100F weather. So I replaced the salmon relay and I've driven it in +100F weather several times now without it ever doing that again, however, I have noticed that sometimes when I am driving in stop-and-go traffic for a long time I notice my yellow cog wheel light comes up. Sometimes it just flashes and if my car is stopped it will go away and sometimes it will just pop up and I can keep driving without any problems (most of the time I try to pull over and turn my car off for a few mins and when I turn it back on the light is gone). I am just wondering if any of you have this same problem or know the exact cause and if I should be worried.
 
#18 ·
I've had the SMG pump replaced twice now. (both under warranty) Initially when the cog light came on the car seemed fine I assumed it was just a random code and booked in to see the dealer, unfortunately as time went by engaging gears in the morning was less and less reliable.

After reading a lot here, and wondering at likelihood of the second pump failure in under a year I enquired if it could be the relay, I was told that while the relay was failing, the cause was the pump drawing too much current, in turn causing the relay to burn out, so a new relay would just mask the issue.

I can't say I trust information the dealers repair centre give me... but this did sound plausible. (but I'm not a mechanic.)

I'd say it's certainly worth pulling your new relay and taking a look at it, along with getting the codes read, and perhaps implementing the heat fix.
 
#20 · (Edited)
Yea they told me it was the pump and I had just bought the car from a reputable dealer and it is under warranty, the dealer said other dealers will sometimes tell you that in order to charge more however it would solve the problem but a pump may not be needed. The car seems to shift fine even in the morning and since the relay was replaced I dont seem to have any gear-shift issues im going to try the resistor mod and hopefully that eliminates the cog light from coming up aka the temp sensor. I guess if it still comes up it would be a faulty pump under which case id take it and get it replaced under warranty. Some other forum users have said that theyve got their pump and relays replaced and the light still comes up in that case it would be the faulty temp sensor, thats why Id rather try everything else first before replacing the pump... thanks for the info
 
#21 ·
I have had the same problem in hot and cold temps. Light comes on however vehicle runs just fine. Most of the time it just goes away after a drive cycle. I do notice that it only occurs in stop and go traffic. When I am running the interstates vehicle runs fine, even under hard acceleration.

Subscribed, hope you find the issue.
 
#22 ·
Hey guys I was able to finally do the resistor mod which took about 30 minutes total and voila the car hasn't dropped out of gear since. I drove it in 90+ degree weather in traffic which it would normally cause the cog light come on and it didn't . It's like a dream come true to not have to fear that dreaded light anymore I would recommend this mod to anyone having similar issues.
 
#24 ·
This mod is a must for SMG M3 owners. Works like a charm. :)
 
#26 ·
Hey guys,

so Captain jinx came back to kick my ass....today I was driving for about 30-40 mins in heavy stop and go traffic and despite the resistor mod the cog light came back again and just dropped me down into neutral at a red light in the middle of traffic (major embarrassment) I also noticed when the car was dead and I turned the key to position one the red section of the coolant temp gauge would light up but as I was driving it never went past the halfway marker at all and as the car was going into neutral at the light the battery icon was flashing. I will try getting the codes read in the next couple days but maybe its possible the battery is failing? thus causing the cooling system to malfunction or maybe I need a new hydraulic or water pump? any suggestions would be great! damn this things has a mind of its own but I still love it to death just gotta find the cause.... thanks guys !
 
#28 ·
I would start with the battery and get it tested and or charged. CPV valve is an easy fix but that shouldn't make you drop out of gears.From what your telling me, i think its electrical. I could be wrong. Just my 2 cents.
 
#30 ·
I currently have 80K miles on the car and yes I think it may be the battery because I also noticed last night that sometimes while im driving the lights in the instrument cluster will kind of flicker a bit and yes I am looking into replacing the water pump as we speak
 
#31 ·
Hey guys sorry its been awhile so I finally got my problem fixed. I had taken it in to BMW again and they were trying to charge me 4300 to install a new hydraulic unit but I had a feeling my hydraulic pump wasnt broken since the problem only happened every now and then so I took it to my mechanic and he discovered that the hose connected to my hydraulic pump was leaking a bit so he bled the system and replaced the hose and voila I drove in traffic for 2 hours this weekend no cog light showed up and the car runs great now feels good to not have to worry about that light showing up anymore! Hopefully some people out there can use this to solve their problem
 
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