Mass air flow sensor

From W220 S-Class Encyclopedia
Jump to navigation Jump to search


The Mass Air Flow (MAF) sensor is also known as the air volume gauge or air mass gauge.

The MAF contains a hot wire sensor and an integrated temperature sensor. For a complete description refer to:

This is what a MAF sensor looks like:

W220 MAF sensor
BOSCH MAF sensor (F00C2G2025)
BOSCH MAF sensor (F00C2G8728) - year 2022

The same sensor (BOSCH F00C2G2025) is used on both M112 and M113 engines. However, the inner diameter for the MAF housing on M112 is smaller (see the comparison below).

MAF housing A1120940048 (M112) and A1130940048 (M113)
MAF housing M112 vs M113

The MAF sensor will foul over time, but the mixture formation can workaround it by adapting the mixture formation. When this adaptation gets out of range, we get the typical mixture codes - such as P0170/3. The degree of "adaption" can be seen using DAS.

The sensor itself does not have MB part number and must be purchased together with the housing A1120940048 (for M112) or A1130940048 (for M113). There are cheap 15 USD Chinese MAF sensors (e.g., sold on FENRIR parts store) and they have proven to be reliable.

  • M112: A1120940048 / BOSCH 0280217515 (100 EUR)
  • M113: A1130940048 / BOSCH 0280217810 (115 EUR)

Cleaning MAF

The Bosch MAFs have a cleaning cycle. During this cycle, the current is briefly increased to the hot wire sensor and this increases the temperature to something like 1000F. This is akin to a self cleaning oven.

To clean a MAF sensor, a special MAF sensor cleaner must be used, which leaves no deposit after drying out. A cleaner will remove oil and such deposits, but in the case of the Bosch MAF units, the deposit is probably more like a hard scale caused by deposits baking on.

Replacing MAF

The MAF sensor is held in place in the MAF housing with two Torx security screws which have a dimple in the center of the screws and hence a special driver is needed.

Torx security screw driver

The following video shows how to replace the MAF housing:

MAF Housing Relacement (By Masood)