Mercedes-Benz W211 fault code air mass too high (2346 / 2355)
What does W211 CDI fault code 2346 or 2355 (air mass too high) mean?
The amount of air measured by the mass air flow sensor (MAF) is greater than the engine control expects. The cause is often in the EGR system (exhaust gas recirculation), because when the valve stays too closed, too much fresh air goes into the engine. The car may go into limp mode and lose power.
What can cause the air mass too high fault and what is checked?
The items to check are the EGR valve, the mass air flow sensor (MAF) and the intake manifold swirl flaps. A sooted EGR valve can stay slightly open or stick, and the flaps can seize from carbon deposits or poor vacuum. Sometimes replacing the mass air flow sensor (MAF) turned off the fault light.
Is cleaning the EGR valve enough or does it have to be replaced?
Cleaning and thin oil sometimes help, but the fault can return, and cleaning is not always enough. Moving the lever by hand does not prove the condition of the valve. The EGR is usually replaced as a complete unit. On the OM642, part number A6421400860 has been confirmed correct; have a workshop do the replacement.