The M272 V6 and M273 V8 were fitted across an enormous slice of the Mercedes range through the mid and late 2000s. Both share a weakness in the same area of the engine, and it produces the same codes.
What fails
On the M272 it is the balance shaft gear. On the M273 it is the equivalent idler gear. In both cases the gear was made to a specification that proved too soft for the working life it was given, and its teeth wear away.
As the teeth shed material, the meshing loosens. Backlash builds. The balance shaft — and with it the timing reference the engine depends on — drifts out of the relationship the control module expects.
The module notices this as a correlation error between camshaft and crankshaft position, and lights the dashboard.
Which cars
M272 V6: C230, C280, C300 and C350, E350, CLK350, ML350, R350, SLK280 and SLK350, GLK350 — across W203, W204, W211, W212, W164 and X204 bodies.
M273 V8: E500 and E550, CLS500 and CLS550, S500 and S550, CL500 and CL550, ML500 and ML550, GL450, GL500 and GL550, R500, CLK500 and CLK550.
The engines appeared from around 2004 (M272) and 2006 (M273).
The dates — and the thing I am not going to pretend about
The period generally understood to be most affected is roughly 2005 to mid-2008 production. Mercedes introduced an updated gear during the run, and engines built after that change are much less prone to it.
Now the honest part, because this is where a lot of articles quietly overstate what they know. You cannot reliably establish from a VIN or a build year alone whether a specific engine has the old gear or the updated one. The changeover was progressive, engines and cars were not built in lockstep, and a car at the boundary can go either way.
The only way to be certain is to look — either at the engine number and the gear itself, or at physical evidence of wear. Anyone who tells you definitively from the registration document is guessing. We would rather say that than give you a false clearance on a car that is quietly grinding a gear away.
The symptoms
The check engine light is usually first, and often it is the only thing an owner notices for a long time.
A rattle or ticking from the front of the engine, most obvious on a cold start and lasting several seconds.
Rough idle, sometimes stalling, sometimes a vibration through the car that is worse once warmed up.
Reduced performance as timing drifts further from where it should be.
The codes are the correlation family — P0016, P0017, P0018 and P0019. Worth knowing: the absence of a code does not clear the car. Early-stage wear can be present with nothing stored.
Why it is a big job
We are not going to soften this. Reaching the gear means getting to the front of the engine and removing the timing cover, which is substantial disassembly and substantial labour.
Because the access is the expensive part, the timing chain, tensioners and guides are normally done at the same time. Putting an engine back together around an old chain, having already paid to open it, is a false economy of the worst kind.
The replacement gear is the updated part — the original specification is not reused, which would simply restart the clock.
We do this work in-house, and we hand back the old gear so you can see the state of the teeth that came out. On a job this size, seeing the evidence matters more than usual.
What it is worth doing about it
If your car is in the affected range and the light is on with a correlation code, get it looked at rather than clearing it. Every kilometre driven with the gear wearing is more debris circulating and more drift in the timing.
If your car is in the range with no symptoms, do not panic and do not preventively open an engine. What is reasonable is to have the codes checked, the oil and filter inspected for metal, and a proper cold start listened to — that is a short, cheap appointment that tells you where you stand.
And if you are buying one of these, this is exactly what a pre-purchase inspection is for. A cold start done first thing, before the seller has run the engine, plus a scan for stored correlation codes, is the difference between a good used Mercedes and someone else’s engine bill. The broader checklist is in 7 checks before buying a used German car in Jeddah.
More on the marque on our Mercedes service page.