Mercedes W222 air mass sensor fault causing limp mode and engine warning light, with multiple intake air temperature and MAF sensor related fault codes. Diagnosis confirmed internal air mass sensor failure.
Vehicle arrived in limp mode with engine warning light illuminated.
Fault codes present relating to air mass and intake air temperature signals, including short circuit to positive and implausible signal faults.
Live data testing was carried out on both air mass sensors to compare readings between banks.
A swap test was performed by moving the suspected sensor to the opposite side of the engine to confirm the fault.
After testing, the fault followed the sensor, confirming internal failure of the air mass sensor rather than a wiring or ECU issue.
On this engine, the intake air temperature sensor is integrated within the air mass sensor assembly and cannot be replaced separately.
The complete air mass sensor was replaced (A642 090 17 42).
After replacement, limp mode was cleared and all fault codes were resolved.
