Modern Mercedes-Benz vehicles come equipped with a rain light sensor. The sensor detects the presence of rain on the windshield and automatically adjusts the windshield wiper speed based on the intensity of the rain, it also automatically turns on the headlights when ambient light reaches a low level.

The sensor requires an adaptation when it or when the windshield is replaced. A sensor needing calibration may set the fault code (B221D49) The rain sensor has a malfunction

Some of the additional fault codes that may set for RLS failures (including physical failures of the sensor) are:
Fault code: B1090 OCP-Overhead control panel - No communication is possible with component 838/2 RLS

Fault code: 9081 D8EOverhead control panel - 838/2 RLS - Communication fault

Fault code: 9080 D8EOverhead control panel - 838/2 RLS - The data line has Short circuit

Fault code: B1081 OCP-Overhead control panel - Component 838/2 RLS signals an internal error

Fault code: B1092 OCP-Overhead control panel - Component 838/2 RLS or the lead has short circuit

Fault code: B1091 OCP-Overhead control panel - No response from component 838/2 RLS

Fault code: B1080 OCP-Overhead control panel - Component 838/2 RLS internal error

Fault code: 90C0 D8E Overhead control panel - 838/2 RLS -Short circuit

Fault code: 9084 D8E Overhead control panel - 838/2 RLS - Not learned

Fault code: 9083 D8E Overhead control panel - 838/2 RLS Internal fault

Fault code: 9082 D8E Overhead control panel - 838/2 RLS Internal fault

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