SMG Pump and No Shifting Issues - BMW M5 Forum and M6 Forums
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post #1 of 24 Old 2nd July 2019, 09:32 PM Thread Starter
MAC_OH
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SMG Pump and No Shifting Issues

Hello

Have a 05/07 (build date) M5 with 95k miles. Recently got in it and got the red gear icon and the car wont start. Scanned the car, cleared the codes and the car will start and shift into gear once or twice before it sounds like a can full of marbles and goes into limp again.

Got the following codes from the SMG system:

CF12, this is a hard code and will not clear
4FA0, code appears after marble in can sound
5103, same as above, will clear but comes back after marble sound

I replaced the electric SMG motor thinking I have a low pressure issue and while the pump sounds quieter it hasn't fixed anything. I can run the pump and build up pressure with my scan tool just fine. As long as I have enough pressure the transmission shifts into 1st and reverse just fine.

The issue is that once the pressure drops the pump stops running and you have to start the process of clearing codes and running the pump manually all over just to move the car.

Any ideas? Thinking it might be the accumulator and or the PLCD sensor or some sort of pressure sensor?

My current scan tool can not do SMG adaptation what scan tool should I get?
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post #2 of 24 Old 2nd July 2019, 10:05 PM
Q.
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It can only be one of three things.

Smg pump
Clutch / flywheel
PLCD

a tell tale sign for the PLCD would be a big puddle of hydraulic fluid on the floor.

If your transmission is banging into gear followed by yellow or red COG, that's ur clutch.

If your PLCD is dead, it wouldn't shift gears at all. In fact, it wont even let u start the engine.

I personally use ISTA/RHEINGOLD to do adaptations. Start with this. If the process fails, do the above.

Best of luck.


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post #3 of 24 Old 2nd July 2019, 11:18 PM
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Quote:
Originally Posted by Q. View Post
It can only be one of three things.

Smg pump
Clutch / flywheel
PLCD

a tell tale sign for the PLCD would be a big puddle of hydraulic fluid on the floor.

If your transmission is banging into gear followed by yellow or red COG, that's ur clutch.

If your PLCD is dead, it wouldn't shift gears at all. In fact, it wont even let u start the engine.

I personally use ISTA/RHEINGOLD to do adaptations. Start with this. If the process fails, do the above.
Not quite...
The PLCD has nothing to do with the fluid side of things so it can't cause a leak. Guessing you meant the slave cylinder.
Don't see how the clutch has anything to do with banging into gear either. It either slips (when worn) or not.

To the OP, post a clip/video of how it sounds, that may help with troubleshooting.

Grinding doesn't sound good, perhaps the pump itself failed. Did you open the pump when replacing the motor?
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post #4 of 24 Old 2nd July 2019, 11:27 PM Thread Starter
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Yea, I didn't think the PLCD can cause a leak

The grinding only happens when you try to shift and there is no pressure in the system. There is no grinding when the pump is primed or there is enough pressure in the system to shift the gears.

For whatever reason the pump runs once and doesn't come back on or doesn't run at all. Not too sure if the pump should run all the time or on demand?
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post #5 of 24 Old 3rd July 2019, 12:57 AM
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Quote:
Originally Posted by MAC_OH View Post
Yea, I didn't think the PLCD can cause a leak

The grinding only happens when you try to shift and there is no pressure in the system. There is no grinding when the pump is primed or there is enough pressure in the system to shift the gears.

For whatever reason the pump runs once and doesn't come back on or doesn't run at all. Not too sure if the pump should run all the time or on demand?
How do you determine what's enough pressure and what's not? The ecu commands the pump on-demand when pressure falls below a threshold (which is temperature dependent). When starting up the car it won't start unless exceeds the threshold. If car is already running and pressure fails to build up only then the system will keep operating until pressure drops to zero.

The ecu stops commanding the pump on if pressure fails to increase in a given amount of time. An error is stored when this happens. If you delete codes then ecu pump control is restored (until it fails again). You can monitor the pressure reading and pump status (on/off) in inpa or ista.
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post #6 of 24 Old 3rd July 2019, 05:55 PM Thread Starter
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So here is how it goes.

I open the door and hear the SMG pump run like normal, it stops in 5-10 seconds. I shift it into gear 1-2 times and it works fine, the car will start and move.

However, if I try to shift it into gear 3-5 times it will start grinding, the pump will never kick on again and the car wont start and move because it can't shift gears. So i get one good pump and shift possible after I clear the codes and then it never runs again. If I watch the pressures on the scan tool it only starts grinding when the system pressure drops very low, too low for it to shift into gear.
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post #7 of 24 Old 3rd July 2019, 06:53 PM
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I think there may be a leak in the hydraulic unit causing pressure issues once running. I found this snippet from Jim:

4FA0 is not always a concern by itself as it can be external o-ring leakage on the cartridge or internal leakage on the spool. This allows pressure to bleed off the slave closing the clutch when the SMG module thinks it should be stationary, thus the 4FA0 "position deviation"

But then you have what seems to be grinding noises and a 5103 which the only reference I found was about supply voltage. The CF12 seems to be a new one. I'll try to look at the ista description. In the meantime it'd help if you try to capture a video of the entire cycle showing pump priming, grinding, and pressure readings while all this happens.
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post #8 of 24 Old 4th July 2019, 12:02 AM Thread Starter
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post #9 of 24 Old 4th July 2019, 01:30 AM
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It's not the pump nor accumulator. Try to charge pressure and then shift straight into 2nd, (skip 1st). My guess is something in the 2nd gear hydraulic circuit is damaged causing a massive pressure loss when activated. Either a shift fork or solenoid goes back and forth as pressure tries to build then drops. Guess it should be obvious once you drop the trans and inspect the solenoids and/or shift pistons.

Small chance this could be a gear position sensor wiring issue, but you can try to wiggle the position harness from below and see what happens.

Do you own that shop?
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post #10 of 24 Old 4th July 2019, 01:40 AM
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Forgot to warn you that insulation will crumble when you wiggle that harness. Either way you'll have to drop the trans anyway so...
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