Here is the solution we have been waiting for someone to come up with,
Credit to Alex Crow an independent Mercedes specialist and member of the Mercedes Benz owners forum.
The M55 is the same 3 wire motor fitted to the om642 CRD engine,
This appears to be the contents of the emulator but only costs coppers.
Inlet port shut off motor delete (CDI2)
A popular mod now, is to disable the inlet port shut off flaps, particularly on 270 CDI (612) engines.
This is usually done because of damage to the flaps from wear and tear, accelerated by EGR gasses.
It is possible to replace the entire manifold, but at significant cost, and some of these cars are old and unloved now!
Even if the manifold is changed, problems can still occur with the actuator motors (M55) jamming and signaling faults to the ECU.
So, how to do without the system...
To remove the flaps is simple, but leaves big holes in the intake manifold.
To plug these holes, I cut short sections of 16mm threaded bar, tap threads in the holes, fit the plugs with superglue, and finally drill and lockwire them for good luck.
With me so far?
But we still have a problem, if the motor is removed, a fault code will be logged, stating 'M55 inlet port shutoff motor signal wire resistance too high'.
Yes, the motor can be left in place and connected to the loom, and if working there will be no fault code.
However, as is often the case, the motor may have heavily worn gears, and frequently jam.
This will log a different code - 'M55 inlet port shutoff motor signals fault through ground keying', which simply means the integrated circuitry in the motor has seen that its mechanism is jamming, and has signalled a fault to the ECU by temporarily grounding out the signal wire.
So, if the motor is worn and jamming, we have a problem, but we do not want to replace it with a new one, especially now there are no flaps fitted.
Getting there now...
So, to cut to the chase, all we need to do to avoid logging fault codes, is wire in a resistor between the signal (PWM) wire and the 12v wire to the M55 motor.I have found that values from 1k to 10k ohms work - 20k ohms is too high.
I have opted for 4.7k ohms on my testbed, and so far all is well - no codes being logged.
I should add that you can buy these mods on ebay http://www.ebay.co.uk/itm/Inlet-port...item1e6a7d237e
, but they are rather more expensive than a 4.7k ohm resistor...
I have now carried out the mod..pics at post no 49.