M272 Camshaft position sensors

When you own a modern Mercedes-Benz, you seem to be playing constant whack-a-mole with the check engine light.   I’ve written before how silly I think the check engine light is, but we’re stuck with it.   Personally, I would just drive older cars, but this is not for everyone and my wife has a 2007 E350 Wagon.    There were two codes this time.

The first set of codes were complaining about the correlation of the camshaft and the crankshaft on one bank.   I had previously changed the magnetic actuators, which temporarily fixed the problem.    If the car didn’t sit outside the engine numbers with the soft balancer shaft, I would have probably assumed that this was my issue.

The second set of codes were about the tumble flaps in the intake manifold.   They are made from plastic and the hot engine makes them brittle and fail.   Mercedes will try and sell you a whole new intake manifold, but there are aftermarket solutions to replace the plastic with metal.   You would have thought Mercedes-Benz would have learned by now about brittle pastic on their engines.   I didn’t want to tackle this one myself, so had it done by a professional.   While the car was there having this and the front suspension rebuilt, we checked the codes.    The various camshaft codes were there, but the actual values of the camshafts seemed correct.

That got me thinking that perhaps it was the sensors sometimes giving bad readings.   I probably should have changed them at the same time as the magnetic actuators.   In any case, the M272 camshaft position sensors are not particularly expensive and very easy to change.

As the M272 is a DOHC engine, there are four sensors.   The right hand sensors are slightly harder to change, but each one can be done in less than five minutes.   The new sensors came with o-rings, which was good as the old ones were very hard.     I don’t know what it was, but there was some kind of residue on a couple of the sensors.   I doubt it was impacting how they worked, but at least the new ones do not have it.

After replacing all four sensors and re-setting the codes, I was able to drive for 15 minutes without the check engine light.   It’s been a long time since that was possible.   The proof of the fix will be if the light is still not illuminated after a couple of weeks.   It was worth trying as four M272 camshaft position sensors are not expensive and the time to change them is negligible.

Update 22/9/21:  The Check engine light is back on.   Only lasted two days.    Back to the drawing board.