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I've seen a number of posts about oil leaking into the connectors for the cam phasers and sensors, so I thought I would check the ones on my car.
I'm not 100% sure if this is more frequently encountered on pre-W212 models but about 30 min effort can verify, so I figured why not.
The basic info is that with the dual overhead cam engines there is a cam phaser (adjuster) and cam sensor for each of the camshafts. Therefore, 2 each per cylinder head 4 total for the car.
The cam phasers take command from the PCM to advance/release the cam depending on operating factors. The cam sensors provide feedback back to the PCM on the actual camshaft position. Both are critical to engine operation and are also correlated with the crankshaft position sensor so the PCM knows where the optimum firing for ignition and fuel should be. If any of these are out of wack, CEL will illuminate and can also cause a misfire code as well.
Anyway, here's some tidbits of info on checking these connectors. Be forewarned - these connectors live in a harsh environment and can get brittle over time/heat cycles, so be as gentle as possible in removing them. It's not the end of the world if one breaks but will require another pigtail connector to be installed into the harness.
MB sells sacrificial harnesses but IMO that's a poor solution to repair a leak. All phasers and sensors can be replaced fairly easily and it's not a huge cost so I personally would opt to do that rather than allow the leak to continue and just plug another harness in.
Here's what that sacrificial harness looks like for the cam phasers (2-wire), part number is 2711500156 for my car. This is oem part made by Delco.
Maybe I missed it somewhere, but I don't seem to find a similar oem version for the 3-wire sensor harness. Aftermarket connectors with pigtail are available though.
Inspection
First off, look at the area and see if there is an oily residue around the components or on the front of the cylinder heads, that's always a good indicator. Oil needs to be inside and not outside of the engine.
In my case, there was no residue but I still wanted to verify condition of the actual connectors. I removed the front of my V6 engine cover and an air inlet tube for the pics.
Here are the 4 connectors on the passenger side, I put a bit of tape on each to show them, 2 on the left and 2 on the right.
Connectors can be a maddening puzzle sometimes. You first unlock these by first carefully pulling the gray clip out slightly. You will hear a click. the picture shows one connector in unlocked position (compare with connector on the right that is still locked). Just comes out about 1/8 in or so.
You then push in on the same gray locktab to be able to then remove the connector. You will hear another click as the tab releases. This is where the brittle ones can break so if that happens you will have to either leave the connector alone or use a pick to release the tab at the base of the connector. This picture is pushing in on the tab just before pulling the connector itself off.
Here are the 2 types of connectors. The top one is a 2-wire connector for the cam phaser and the bottom one is a 3-wire connector for the cam sensor. I believe but haven't verified that the cam phaser wiring is power and ground and the cam sensor is power, reference signal, and ground. Note in this case they are clean, no oil.
Once you have verified condition, they can be reinstalled, reverse of removal. I use a bit of dielectric grease around the connector just to make connection smoother. When you install the connector itself, you will hear a click to verify full connection. Then when you push the gray tab back in you will hear another click to verify locked in place. Also, go slow on inserting the connector to ensure that it's going in straight and no pins are being bent.
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