E46 M3 SMG Issue

[J~~ 0]

Hi team,

I've had my M3 for over a year now and everything seemed fine and Im loving the car but recently the SMG COG came on. This worried me abit but car was still driving/shifting fine. Few days ago i was slowing down for a traffic light and the SMG tried to auto downshift from 2 to 1 but the 1 only blinked once or twice and then the gear showed a solid 2 again. The weird thing is that I couldnt put the car in neutral or go into any other gear and the car wouldnt accelerate. I turned the car off and waited for the gear number to go off and turned the car back on again and it was shifting normal again. Tonight i was coming off the motorway offramp and the same thing happened agin this time from 6 to 4. Same symptom as before it was stuck in 6 with no power but car was still idling. i have replaced the salmon relay the COG light went away for about 10kms then came back on and I have unplugged the battery for an hour to reset SMG and COG light stayed off for couple KMs. Any one else know what could be causing this? Where could I take it in Auckland who has experience working on SMGII?

 

Thanks in advance 

Edited November 20, 2018 by J~~

[BM WORLD 1283]

my guess is the smg pump motor brushes worn out and not enough fluid pressure is being made.

have spares if needed

but get it checked out etc , can also be worn clutch and parts around it etc.

 

can scan it too if you like 

Edited November 20, 2018 by BM WORLD

[J~~ 0]

Would it be possible it’s behaving like this due to low SMG fluid? When I unlock my doors and wait for the pump to prime then check the reservoir the fluids showing just above the bottom of the dipstick but if I unlock the car and let it sit for 10mins the fluids showing near the Max line which one is the accurate one?

[BM WORLD 1283]

low fluid will cause issues too ,  so where has it gone though??

[M3_Power 636]

On 11/21/2018 at 8:06 AM, BM WORLD said:

my guess is the smg pump motor brushes worn out and not enough fluid pressure is being made.

have spares if needed

but get it checked out etc , can also be worn clutch and parts around it etc.

 

can scan it too if you like 

Doubt it would be a brush issue

If pump motor fails to build pressure it will go into neutral and fail to engage any gear usually. The symptoms sounds like it is getting pressure resistence so it does not go up or down (1 and 4) along the travel but it rotates fine.

four possibilities by what you have described - gearbox readaptation required as it is struggling to find the correct gear so it is experiencing resistance beyond the maximum value for it to travel up or down (ie north south engagement) but not left or right or vice versa.

temperature sensor issue on the smg pump unit - these fail like the rear subframe and if experiencing high temperature you will get temperamental issues with gear engagement. But the programming for this in the module is for it to drop into neutral so unlikely.

Third possibility - broken indent spring in the gearbox (one of three but likely one only) - very possible as you described 1st gear and that’s the big indent spring on the top of the gearbox and that breaks all the time. 

Lastly clutch issue so the clutch isn’t disengaging completely for the gearbox to engage gears - most likely if the clutch is old - most likely failure is the cheap plastic pivot pin on the clutch release fork - when this fails the clutch does not diaengage 100% (more like 60%) with the clutch fully in ... this will result in pressure resistence in the system and cause it to not engage selected gear.

My money is on the last one if old clutch.

A scan and readaptation will tell you exactly what is wrong.

 

Edited November 23, 2018 by M3_Power

[M3_Power 636]

On 11/21/2018 at 10:25 AM, BM WORLD said:

low fluid will cause issues too ,  so where has it gone though??

No it doesnt that reservoir is exactly that an expansion tank. Unless it is completely empty it won’t cause an issue.

Get INPA and get live readouts of the pump pressure and temp ect it will give you all the readings you need to see including adaptation readings for each gear. 

If you don’t know what you are looking it bring it to me or take it to Ray at Hellbm.

Edited November 23, 2018 by M3_Power

[Cammsport 390]

Did you get to the bottom of this issue J?