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ok, here's how it works ...
the variocam system in your car allows the cam profile to change with rpm.
this is accomplished by joining the cams together with chains. an actuator pushes on pads that tighten/loosen the chains to change the cam profile.
the position of the cams relative to each other is monitored by a sensor. this sensor measures cam 'deviation'.
Porsche spec is max 6 degrees deviation, but ECU doesn't throw a code until around 9 degrees (I think).
deviation can increase as the pads noted above wear down. this is a known issue with these cars and evidence of the wear can be seen in gradually increasing deviation as well as green flecks of plastic in the oil filter. there is thought that the chains slapping on the pads during start-up ('start-up rattle') is a big culprit in pad wear.
another known issue with these cars is failure of the sensor; often actually the wiring to the sensor.
the code you received is often associated with the latter issue; as posted by jfp - short to ground, open circuit.
first step is to confirm wiring and replace sensor. it sounds like you replaced sensor - was wiring checked also? was deviation checked before the change?
next, the sensors are sensitive to how they are installed - a poorly installed sensor can give an iffy deviation reading. you have a deviation reading now of 9; did they get a deviation reading from the old sensor before they replaced it? you see, if they couldn't get a deviation reading before the change that means sensor or wring was bad. or they inspected and determined that sensor or wiring was bad and replaced them. what are the odds that you had a bad sensor/wiring, only to determine that your deviation is off after replacement? MUCH more likely that the replacement sensor is off in some manner.
otherwise, this is where a durametric is a great asset - you can regularly check deviation with it, to determine if any change in deviation is sudden (most likely sensor failure) or gradual (pad wear).
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