Hi, Can anyone give me some info on this vehicle, vehicle was presented to me by another garage as a non-runner. I decided that there must be some issue with the valvetronc mechanism or eccentric shaft sensor, having very little data on this we took of the cam cover and found that the eccentric shaft actuator motor had seized (we applied a feed to the motor and had no response)by turning the motor manually we got it out and bench tested it and it worked fine. I checked the eccentric shaft and that turned OK as well, so we replaced everything and the engine fired up and seamed OK. After road test however we keep getting fault code (2A61 Valvetronic, adaption.)coming up, any advice would be greatly appreciated,and any info on checking eccentric shaft sensor.
Re: BMW 120
Posted by Dave Harney on May 14, 2010, 2:25 pm, in reply to "BMW 120"
Variable valve timing gear / Valvetronic
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 unit from the position of the accelerator pedal and other variables. The variable valve gear is moved by its own control unit 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 unit and Valvetronic control unit is on a separate LoCAN bus. All functions are calculated in the engine control unit. The Valvetronic control unit 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 unit in digital form.
The Valvetronic control unit powers both potentiometers with a voltage of 5 V.
Monitoring the signal voltages The Valvetronic control unit 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 unit 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 unit is unable to communicate with the Valvetronic control unit 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
Variable valve timing gear / Valvetronic :
Learning the stop positions 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.
After the learning procedure has been initiated via the DIS-plus Tester, a brief adjustment sound can be heard in the engine compartment. The DME reports whether the adaptation has run correctly or not.
For learning the stop position, faults can also appear in the fault code memory of the DME; there is a test module for this.
You can trim a sheeps wool many times, but you can only fleece it once !
Re: BMW 120
Posted by Mark Robins on May 14, 2010, 2:56 pm, in reply to "Re: BMW 120" Mark Robins
Thanks for that Dave, I guess it's (hopefully) just a matter of driving it fot it to re-learn it's settings.
Re: BMW 120
Posted by Keith Simpson on May 14, 2010, 6:41 pm, in reply to "Re: BMW 120"
Why I Man
Fixed #
Posted by Mark Robins on May 17, 2010, 9:01 am, in reply to "Re: BMW 120" Message modified by board administrator May 17, 2010, 2:16 pm
The road test fixed it, now the question is why did the eccentric shaft motor stick in the first place? We will see what happens when the customer uses it!
on May 14, 2010, 2:25 pm, in reply to "