Dealing with a startup rattle and persistent check engine lights on your Mercedes Benz 2012 E350 can be frustrating. For owners of the 2012 Mercedes Benz E350, these issues can sometimes point to camshaft alignment problems. This article details a DIY approach to address a specific issue related to the cam sensor wheel, potentially resolving startup rattles and check engine light errors on your Mercedes Benz 2012 E350.
The journey began with the aim to get a Mercedes Benz 2012 E350 smog compliant and eliminate a persistent startup rattle. After some troubleshooting, the focus shifted to the camshaft sensors. Upon removing the intake manifold – a task that becomes quicker with experience, taking only about 30 minutes – the cam sensors were accessed for inspection. Specifically, all four cam sensors of this Mercedes Benz 2012 E350 were pulled to check the alignment marks.
Alt text: Close-up view of cam sensor inspection point on a Mercedes Benz E350 engine, highlighting alignment marks.
The driver’s side, left bank cam sensor window revealed a slight misalignment. Despite careful timing chain installation previously, the cam appeared to be off. This led to consider the possibility of the cam sensor wheel shifting on the camshaft itself – a known issue in some cases. To investigate this on the Mercedes Benz 2012 E350, an experiment was conducted.
Using a large, flat-blade screwdriver (18 inches long with a 1/2-inch wide blade), pressure was applied through the sensor hole to the cam sensor wheel. Initially, it seemed fixed, but with increased pressure, the wheel moved, confirming the suspicion. The engine was rotated until the adjuster wheel could be nudged back into a better position. After several engine rotations, the cam sensor window indicated improved synchronization, although a slight offset remained, potentially due to relaxed tension from lower oil pressure with the engine off. This test suggested that the cam sensor wheel on the Mercedes Benz 2012 E350 camshaft could indeed be adjusted without full disassembly.
Alt text: DIY mechanic using a long screwdriver to carefully adjust the cam sensor wheel position through the sensor hole on a Mercedes Benz E350 engine.
Following this adjustment, the intake manifold was reinstalled, and the engine was started. The result was immediate: a quick start, no startup rattle, and crucially, no check engine light illuminated on the Mercedes Benz 2012 E350 dashboard. A scan tool confirmed that the cam was now in sync and all systems were functioning correctly.
This experience suggests a potential cause for cam sensor misalignment in Mercedes Benz 2012 E350 models: the press-fit cam sensor ring. Mercedes likely uses a press fit for this ring, but being thin metal, it may not be exceptionally robust. A failing camshaft adjuster, known for rattling and hammering noises during engine operation, might contribute to moving the cam sensor plate on the camshaft over time due to its vibrations. Replacing the faulty adjuster, as done in this instance, could prevent further movement.
While the long-term stability of this fix remains to be seen, the force required to move the sensor wheel with a screwdriver implies it is reasonably secure. Without the repeated “hammering” from a bad adjuster, the wheel may stay in place. If future issues arise, camshaft replacement remains an option. However, this quick fix offers a potentially effective solution, especially after addressing a faulty cam adjuster. This entire repair process, after initial valve cover work, took under two hours, highlighting it as a potentially time-saving approach for addressing cam sensor wheel misalignment on a Mercedes Benz 2012 E350.
Alt text: Clean engine bay of a Mercedes Benz E350, showcasing successful DIY repair and no check engine light indication.
This method might be considered a less conventional or “bozo fix” by some. However, the immediate results are undeniable: the Mercedes Benz 2012 E350 is running smoothly, quietly, and without check engine lights. While a more permanent solution like pinning the sensor plate to the camshaft was considered (and might be explored if the issue recurs), for now, this adjustment has proven effective. Considering the cost of a new camshaft and the possibility of future failures, this DIY fix provides a practical and efficient resolution to a common problem in Mercedes Benz 2012 E350 vehicles.
