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onlyonechop 10-18-2012 09:30 AM

Valvetronic power supply undervoltage
1 Attachment(s)
I have a 2006 530xi Wagon with 105k miles on it. I keep getting the following error code: 2A3F Valvetronic, servo motor : power supply.

I checked the continuity between the connector at the VVT servo motor and the computer, and it was fine. I deleted the error two days ago then checked and cleaned the connections to the VVT servo motor and the eccentric shaft sensor. I also swapped out the VVT relay with the DME relay (they are the same part). I checked the codes again and the same error was back and apparently it had occurred 22 times :dunno: in the last two days.

This makes me think that the valvetronic system isn't working at all, which might explain why my gas mileage is so bad. Does anyone have any ideas? I'm thinking it might be the VVT motor, but I don't want to start throwing new parts and $ at the problem and hope something works.


boramkiv 10-18-2012 03:33 PM

Im not familiar with INPA, but IIRC with the Bav Tech tool using actual values I was checking the actual position on the eccentric shaft with a nominal position
based on throttle input. It could only be done with the engine running (I think). I had the car in accessory mode and throttle movement reads, but the Servo
stays at rest, so I had to start it after carefully putting the servo back in (scary). Remember if the Servo fails all together the throttle plate swings into action. To see if the Servo is failing slowly maybe you could check if it can go to WOT, hold steady at increments for periods of seconds with no movement, moves as rapidly as throttle inputs, and returns to rest fully. These are
just guesses as I cannot find anything regarding Valvetronic failures other than the servo just fails all together (which is rare supposedly). Maybe a Bently Manual is in order. I'm not sure if you can read values with INPA.
Good Luck

boramkiv 10-18-2012 03:48 PM

I would say it's likely the sensor. If the car runs all the way up the rev range and its getting 22 faults, i'm thinking the DME is missing info from the sensor rather than
the servo not complying in any part of the rev range. See here though:

onlyonechop 10-23-2012 08:24 AM

Thanks for the info boramkiv.

I haven't had time lately to mess with the problem, but hopefully today after work. I have an idea to see if it is the sensor. If I can find in INPA where I can check the eccentric shaft position, I am going to manually turn the the VVT motor with a hex key and see if the values change. If I do see a change in the shaft position I'll assume the sensor is fine.

I did have a minute yesterday to do a little experiment. Using a hex key I turned the VVT motor clockwise until it stopped. I'm pretty sure this adjusts the eccentric shaft so the intake valves are completely closed. Then I tried starting the car, which wouldn't start. Makes sense if the intake valves are closed. Then I turned the VVT motor counter-clockwise all the way and I was able to start the car without any problem.

boramkiv 10-23-2012 08:58 AM

This is good news for me either way, thanks!
I had this crazy notion that because the servo
looks like a motor that spins around all the way,
when you install it if its too far down for closed valves
or too far up for WOT, the computer would bring it
down or up on its own. I thought that could be a way
to control idle.

That's what I was worried about when installing. You
would think as advanced as the system is it would sort
itself out on its own. There's no idle control valve so WTF!?
Leave it to BMW to keep info glued to themselves to fix.
Good that you can adjust the hex key to get it right
which I figured was possible anyway.

My nominal value is a little off from my actual value with
the eccentric shaft, but I'm idling fine and revving to redline
no problem. So I don't know why that is. Thanks for the

Karriyocc85 02-11-2016 04:56 PM

Hello, my name is Carlos I don't speak to much English. But I think I can help you. I have a 2005 545i and I i was the same problem and I fix,

dl123 09-07-2016 10:46 PM


Originally Posted by Karriyocc85 (Post 9524289)
Hello, my name is Carlos I don't speak to much English. But I think I can help you. I have a 2005 545i and I i was the same problem and I fix,

Hello, can you tell me how you fixed the issue?

Don2007530i 02-07-2017 05:52 PM


Originally Posted by Karriyocc85 (Post 9524289)
Hello, my name is Carlos I don't speak to much English. But I think I can help you. I have a 2005 545i and I i was the same problem and I fix,

Hi all,

New member here and i recently got a fault code for Valvetronic issues . 2A3F

530i a few days ago went into limp mode and can't rpm past 20000 then now car won't start.

Can anyone yelp me with fix advice here, please?

fdriller9 02-07-2017 07:49 PM

I'm not sure for E6x but E9x VVT motor gets power directly from the battery and is passed through the non-replaceable fusible links on top of the battery. Check if the fuse is blown

Don2007530i 02-07-2017 08:22 PM

Thanks, fdriller. You are correct in that i have an e60 with N52 engine and it has VVT.

Indy ran a code for 2A3F, and. I believe he disconnected something from the time AAA dropped my car off to them and next day when I came to speak with him.

Is this a serious problem I should be worried about or can I fix this myself?

My 530i was in limp mode with almost no acceleration but had no problems starting/firing up prior to this morning when I met the Shell Station Indy mechanic.

Will check fuse and report back.

Btw, which fuse in the trunk do I check?

toga94m 02-08-2017 07:19 AM

2 Attachment(s)
From the WDS for N52 engine, it looks like fuse F07 is under the hood, near the VVT relay -

Don2007530i 02-08-2017 08:25 AM

Thank you, toga94m.

Going to get my 530i to run again today. Taking 2 days off work already just having to deal with this.

If am able to get the 530I to start again and have that throttle power again, will i need to reset the battery and/or valvetronic? Is the something I can do or do I need bmw's scan tool?

toga94m 02-08-2017 09:43 AM

The last paragraph of this writeup (also in the WDS) makes it sound like it'll retrain itself, if it detects a major difference from previous conditions.


Variable valve gear/Valvetronic

The variable valve gear was developed to reduce fuel consumption.

The air volume supplied to the engine is not set by the throttle valve but by the variable stroke of the intake valve. An electrically adjustable eccentric shaft uses intermediate levers to change the effect of the camshaft on the rocker arms. This produces an adjustable stroke of the valves.

The throttle valve is now only used for starting up and for emergency operation functions. In all other operating states, the throttle valve is opened so far that it only has a very slight throttling effect. For tank ventilation, a certain vacuum is still necessary.

The corresponding position of the variable valve gear is calculated in the engine control module from the position of the accelerator pedal and other variables. The variable valve gear is moved by its own control module and servomotor. The servomotor is fitted to the cylinder head and it drives the eccentric shaft via a worm drive in the oil chamber of the cylinder head.

The communication between the engine control module and Valvetronic control module is on a separate LoCAN bus. All functions are calculated in the engine control module. The Valvetronic control module evaluates the signals of the position sensor and controls the servomotor of the eccentric shaft.

Position sensing
The current position of the eccentric shaft is sensed by a special position sensor. The sensor is equipped with two independent angle probes. The engine management controls the position by means of the electric drive until the current position corresponds to the set position. For safety reasons, two angle probes with opposing characteristic curves are used. The two signals are sent to the Valvetronic control module in digital form.

The Valvetronic control module powers both potentiometers with a voltage of 5 V.

Monitoring the signal voltages
The Valvetronic control module permanently monitors the two voltage signals of the potentiometers. The monitoring function checks whether the voltages are within the permissible range, i.e. whether there is a short-circuit or sensor defect.

The two signals must not deviate from each other.

In the event of a fault occurring, the eccentric shaft is set to maximum possible valve opening. The air volume is now restricted by the throttle valve. If it is not possible to detect the current position, the valves are opened to the maximum without control.

Monitoring the eccentric shaft position
The Valvetronic control module continuously checks whether the actual position of the eccentric shaft corresponds to its set position. This makes it possible to determine when a valve is sticking. In the case of an error here, the valves are opened as wide as possible and the air supply is controlled by the throttle valve.

If the engine control module is unable to communicate with the Valvetronic control module due to a LoCAN bus fault, emergency communication is set up across a separate line (P_VVTEN).

Learning function/adaptation
In order to achieve the correct valve opening height, all the tolerances in the valve gear must be balanced by an adaptation. In this learning procedure, there is a slow approach to the mechanical adjustment limits of the eccentric shaft. The positions thus reached are stored and used in each operating point as the basis for calculating the current valve stroke.

The learning procedure runs automatically if, for example after a repair, a difference between the last stop position and the new starting position (with terminal 15 on) is detected. The adaptation can also be requested via the DIS-plus Tester.

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