Mercedes-Benz Camshaft Adjuster Magnets – How do they work?


Variable valve timing is installed on most new cars today in order to take advantage of the benefits of both a high performance engine setting, as well as a high efficiency engine setting.  By having an engine that can mechanically alter valve timing on the fly, you can get the best of both worlds.  That makes the lead-foots happy, as well as the environment.  However, when you have critical engine components such as camshafts shifting around, you need a device called a solenoid to control them.  A solenoid is little more than a plunger that extends so a task can be completed.  In the case of several Mercedes engines, these solenoids are also referred to as Camshaft Adjuster Magnets, and if you are here, you may be experiencing an issue with them. This system is not to be confused with Camtronic, which physically shifts a camshaft with multiple cam profiles along a splined shaft to alter lift and duration, in addition to timing.

Camshaft Adjuster Magnets – How do they work?

See the illustration below.  To change cam timing, the electromagnet (Y49/4) activates and pushes a metal rod into the end of a tiny perforated hydraulic ‘control plunger’ (2/2 and 2/3).  The control plunger has a raised sealed ridges, and grooves that are pressurized with oil.  In the activated position, the perforated tube directs oil pressure up and out through one particular series of holes in the (2/5) ‘control valve’, which travels through the corresponding oil gallery and up into the cam adjuster to shift it into position B, advancing timing.   When the magnet de-activates, the spring (2/4) pushes the plunger (2/3) back. The series of holes getting oil pressure changes, and the adjuster switches the position of the cam gear (3) relative to the camshaft (4) for position A.

Early style Camshaft Adjuster Magnets

M271 Camshaft Adjuster Magnets

Don’t forget to buy an o-ring and rubber oil plug

The early style all-metal adjuster magnet can be found on the M111, M104, M119, and M120. These engines went into tons of cars, so this part is fairly common.  When the M271 came out, the VVT system and the camshaft adjuster magnet units got a slight upgrade.

In North America, the only Mercedes that used an M271 4cyl engine was the W203 C230.  The camshaft adjuster magnet on all of these are found on the front of the engine (facing the radiator) and are relatively easy to access.  Commonly they develop internal leaks that gets into the electronics.

Much like the issue with the 722.6 automatic transmission valve body electronics, the oil then is wicked up by the wiring and can fill connected wiring harnesses with oil.  That causes all sorts of issues depending on how far it gets.  The solution is actually quite cheap and easy, they simply bolt on the front of the cylinder head as outlined in this great video.

Buy Camshaft Adjuster Magnet for M111, M104, M119, and M120 engine – 1190510077

Buy Camshaft Adjuster Magnet for M271 engine – 2710510177

M272 Camshaft Adjuster Magnets – Get Price

M272 Camshaft Adjuster MagnetsEven though the w272 camshaft adjuster magnet solenoid is very similar, these commonly cause different problems than the M271 variant found in the second generation C-class.  Since the V6 engine has two cylinder banks, you will have two of these bad boys on each side, making four in total, and four corresponding  cam position sensors.  Early serial number engine actually shipped with a defect in these, causing them to fail prematurely.  The part has since been updated, but they still do fail time to time and it’s important to keep an eye out for the warning signs (and not confuse them with issues caused by the variable length intake manifold).  When the magnet fails, you will come across some driveability issues as the computer is signalling to switch valve timing (but it can’t) so the numbers go out of whack and you get a check engine light.

The Check Engine light will be very specific as to which magnet you are looking at.  For example P0015 is Camshaft Position B – Timing Over-Retarded (Bank 1).  This means the cam sensor is looking for an advanced cam timing, but since the camshaft adjuster magnet never extends to advance the timing, the computer is deducing that the camshaft timing in Position B is too retarded.  Position B refers to the cam (exhaust) and Bank 1 refers to which side of the engine it is.  There is a code for each camshaft and whether or not the timing is reading too advanced or too retarded.

M272 camshaft adjuster magnet

One of the 4 camshaft adjuster magnets found on the M272

You can test these magnets by applying 12v of electrical current to the contacts and listen very closely to hear if the solenoid clicks.  If nothing happens, try on a different sensor.  If nothing happens on all of them, you are probably doing something wrong.  If one clicks and one doesn’t, you know which camshaft adjuster magnet you are looking to replace. If you are getting codes that read “Camshaft position correlation” such as P0017, more than likely a bad camshaft position sensor, the other integral part of this operation.  Here is a list of codes that can be related to the Camshaft Adjuster Magnets, or the Camshaft Position Sensors

P0010 “A” Camshaft Position Actuator Circuit (Bank 1)

P0011 “A” Camshaft Position – Timing Over-Advanced or System Performance (Bank 1)

P0012 “A” Camshaft Position – Timing Over-Retarded (Bank 1)

P0013 “B” Camshaft Position – Actuator Circuit (Bank 1)

P0014 “B” Camshaft Position – Timing Over-Advanced or System Performance (Bank 1)

P0015 “B” Camshaft Position -Timing Over-Retarded (Bank 1)

P0016 Crankshaft Position – Camshaft Position Correlation (Bank 1 Sensor A)

P0017 Crankshaft Position – Camshaft Position Correlation (Bank 1 Sensor B)

P0018 Crankshaft Position – Camshaft Position Correlation (Bank 2 Sensor A)

P0019 Crankshaft Position – Camshaft Position Correlation (Bank 2 Sensor B)

P0020 “A” Camshaft Position Actuator Circuit (Bank 2)

P0021 “A” Camshaft Position – Timing Over-Advanced or System Performance (Bank 2)

P0022 “A” Camshaft Position – Timing Over-Retarded (Bank 2)

P0023 “B” Camshaft Position – Actuator Circuit (Bank 2)

P0024 “B” Camshaft Position – Timing Over-Advanced or System Performance (Bank 2)

P0025 “B” Camshaft Position – Timing Over-Retarded (Bank 2)

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3 thoughts on “Mercedes-Benz Camshaft Adjuster Magnets – How do they work?
  1. Andrew Harvey

    This is such a great explanation for what this part does I just had this problem and ordered a replacement part from your website .
    I had the new cam magnet installed in 20 minutes and now my check engine light is gone. The stealership wanted to do a $2,000.00 repair and rip the camshaft apart I said no thanks and researched the problem its very common to go bad on this SUV ML350 thanks for posting my issue.

  2. Nkululeko Fuyane

    I have a C230 1999 which we just did the engine, its got some chatter noise and sluggish power. After going through the threads here, I am tempted to think I ‘ve the magnet solenoid issue.

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