Varicam not varying? Or is it?

[wdonovan]

2002 C4 Cabrio. Threw code P0349 "Camshaft position sensor 2 Open circuit" and check engine light. CEL went out after 2 days, and the varicam works sometimes. OK, seems likely that there is an intermittent wire or sensor issue but.....

I took data with Durametric. Both banks, cam specified and actual angles, also RPM to see where the actuators moved the cam. I have included the XL graph. It confuses me. It shows both banks doing the same thing, apparently correctly. At the time I shot this data snap, the varicam was definitely not working (It's easy to feel). Any thoughts?

Also other question regards replacing the sensor and/or replacing the wiring. My electronic PET shows what looks a cam angle sensor mounted on the TOP of the REAR end of the right side cylinder. A photo I have of a supposed 2002 996 engine shows the sensor (I think) on the FRONT of the FRONT end of the right side cylinder head. Which is it? Did this change from 02 to 03 or something?

One more.... Is this sensor accessible or must I remove the body off the rolling chassis?

[RFM]

996 MY 02 and 03 are different, the sensor on top of cyl. 4 is a cam angle sensor. What you need are the actuators located in the camshaft covers near spark plug 3 for bank 1 and near spark plug 4 for bank 2. You can check them easily, disconnect the connector - take a 12 volt source - connect the + of the source with the actuator - let the engine idling and connect the - of the source intermittent with the actuator, if you can hear a difference in engine idle smoothness ( rougher ) the actuator is OK electrically and mechanically. If there is no difference in idle pattern, shut off the engine and let the ignition on - do the same as above - if you can hear "tic tic tic" the actuator is electrically OK but mechanically faulty. In fact the PIWIS tester does the same but quicker. Hope it helps.

[wdonovan]

Thanks R! I thought they moved things around between 02 and 03. I just got an updated Durametric software and it has a feature called something like Build Mode. I believe it is a way to force actuators to a given state. I'm going to see if this could advance / retard the cam. It would beat laying on the floor, fiddling under a hot engine.

I am surprised that your bet is on the actuator rather than the sensor. The code seemed to indicate a no signal condition. I was kind of hoping for a bum sensor rather than a stuck actuator. Last one had to be taken apart and the debris screen (which provided its own debris by disintegrating) removed. Wasn't cheap.

[RFM]

Start with the activator check, if it looks OK clear the fault code and drive the car as usual till the code comes back ( if she ever comes back ). Spontaneously occurred problems with the sensor or wiring are not really common but are still possible. Give it a try, you can replace the sensor all the time, in spite of his unpleasant possition with the water hose in the way.