BMW Rain Sensor Calibration

BMW Rain Sensor Calibration [Full Guide]

In today’s post, I’ll cover when, why, and how to calibrate the rain sensor on most BMW models. 

When is the initialization necessary?

In the following cases you’ll need to re-calibrate the rain/light (solar) sensor:

  • After the windshield replacement
  • After the rain/light/solar sensor replacement
  • After replacing the optics of the rain/light sensor
  • After installing the used rain/light/solar sensor

How Does Rain (Light/Solar/Condensation) Sensor Work?

The rain sensor is integrated into a compact module together with light, solar, and condensation sensor (depending on the vehicle equipment).

No.ExplanationNo.Explanation
1Rain, light, and solar sensor2Flexible printed circuit board with a condensation sensor

RAIN SENSOR

The rain sensor evaluates the degree of reflection from the windscreen using transmit and reception diodes (infrared). Measurement pathways are formed by combining transmit and receive diodes in pairs. These measurement paths are used to detect the rain intensity.

Rain sensor system: Rain detection is based on the infrared light reflection where the windscreen glass meets the air. The amount of reflection is affected by how filthy and wet the windscreen is. The infrared light is totally reflected if the windscreen is dry and clean. The reflection is diminished when the windscreen is filthy or wet from the rain.

LIGHT SENSOR

The light sensor detects the brightness of the frontal light as well as the ambient light.

Vehicles manufactured prior to September 2008:

If the car has a head-up display, the brightness of the display is additionally controlled by a customized light sensor.

Vehicles starting in September 2008:

A separate photosensor regulates the brightness of the Head-Up Display if the car is equipped with one.

Rain/light sensor system: The following sensors make up the rain/light sensor system.

  • Ambient brightness sensor (environment)
  • Frontal light sensor (near field)
  • Sensor for controlling the brightness of the head-up display

The rain/light sensor system broadcasts the driving light status (i.e., driving light ON or OFF, the reason for activation) through the LIN bus in a 20-millisecond cycle. The signals in the related CAN message are accepted by the JBE control unit, FEM control unit, or BDC control unit, and sent periodically (signal values unchanged) or when triggered by events (signal values changed).

SOLAR SENSOR

The solar sensor is employed in the integrated automatic heating and air conditioning system (IHKA) for a variety of purposes. The solar sensor detects how bright the sun is on the car.

Solar sensor system: Solar irradiation is taken into account by the automatic climate control unit thanks to the solar sensor. The sun’s intensity on the driver’s and passenger’s sides is measured individually.

CONDENSATION SENSOR

Before the driver observes any fogging tendency, the condensation sensor guarantees fast recognition of incipient condensation for the integral automated climate control. Without the need for the driver to intervene, countermeasures can be implemented early on. The condensation sensor is only active in the integrated heating and air conditioning system’s automated program.

System for detecting condensation: The following data is provided by the condensation sensor:

  • The temperature on the inside of the windscreen
  • Humidity on the inside of the windscreen 

In the automatic program, the climate control unit (IHKA) uses this information to prevent condensation on the windscreen.

The rain-light-solar-condensation sensor is connected to the junction box electronics (JBE), front electronic module (FEM), or Body Domain Controller (BDC) through a local interconnect network bus, depending on the series. The rain-light-solar-condensation sensor is powered via terminal 30B.

The mirror base has a rain-light-solar-condensation sensor. A holding spring holds the rain-light-solar-condensation sensor in place on a mounting plate. The mounting plate is secured to the inside of the windscreen with a strong adhesive. A silicone gel on the optical element establishes the optical link of the rain-light-solar-condensation sensor to the windscreen.

Rain sensor coding

Junction box electronics (JBE) vehicles:

During a restart, the JBE control unit compares the rain-light-solar-condensation sensor’s encoding data to the goal encoding data in the control unit. The junction box electronics control unit executes automatic encoding of the rain-light-solar-condensation sensor in line with the target encoding data in the event of deviations.

Front Electronic Module (FEM) or Body Domain Controller (BDC) vehicles:

During a restart, the FEM control unit or BDC control unit sends a configuration telegram to the rain-light-solar-condensation sensor for vehicle-specific configuration.

The automatic driving lights control allows you to modify the sensitivity settings by encoding them.

Rain Sensor Calibration (Initialization)

The rain sensor must be matched to the windscreen (initialized) if the sensor or windscreen is exchanged in order to assure proper functioning of the optical measuring procedure for the detection of precipitation.

The windscreen glass must be dry, clean, undamaged, and free of flaws in the rain sensor region to ensure flawless initialization.

The ISTA system’s “Initialize rain sensor” service function is used to perform the initialization. This service operation updates the rain sensor’s adaption values. I’ve done it countless times and never had any complaints. 

There are also other, alternative tools to calibrate the rain sensor like Snap-on. 

The Table of Additional Work After Replacing Rain Sensor

  • 1-Series: E8x
  • 3-Series: E9x
  • 5-Series: E6x
  • 6-Series: E6x
  • X1: E84
  • Z4: E89
Sensor type/Sensor shapeWith windscreen replacement sensor requiredWhen replacing the sensor/Programming/encoding necessaryWhen replacing the sensor/Initialisation requiredConnecting the diagnosis system required
Condensation sensorsquare 30 x 20 mmYesNoNoNo
  • 5-Series: E6x
  • 6-Series: E6x
  • 7-Series: E6x
Sensor type/Sensor shapeWith windscreen replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing substitute visuals Programming/encoding is necessaryWhen replacing the sensor/substitute visuals Initialisation requiredConnecting the diagnosis system required
all typessquare60 x 40 mmNoYesYesYes
RLS approximately ø 50 mmNo(new substitute visuals required, refer to Electronic Parts Catalogue)NoYesYes
  • X5: E70
  • X6: E7x
Sensor type/Sensor shapeWith windscreen replacement, replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing substitute visualsProgramming/encoding is necessaryWhen replacing the sensor/substitute visualsInitialisation requiredConnecting the diagnosis system required
RLPSS (Rain, light, and precipitation solar sensor)(Designation is located on the back of the sensor)approximately ø 50 mmYesYesYesYes
RLS (vehicle with no HUD)(Designation is located on the back of the sensor)approximately ø 50 mmNo(new substitute visuals required, refer to Electronic Parts Catalogue)NoYesYes
RLSS (vehicle with HUD)(Designation is located on the back of the sensor)approximately ø 50 mmYesYesYesYes
  • 1-Series: E8x
  • 3-Series: E9x
  • X1: E84
  • X3: E83
  • Z4: E89
Sensor type/Sensor shapeWith windscreen replacement, replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing the sensor initialization requiredConnecting the diagnosis system required
all types square 60 x 40 mmNoYesYesYes
  • 5-Series: F1x
  • 5 Series GT: F07
  • 6-Series: F06, F1x
  • 7-Series: F0x
  • X3: F25
  • X4: F26
Sensor type/Sensor shapeWith windscreen replacement, replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing substitute visualsProgramming/encoding is necessaryWhen replacing the sensor/substitute visualsInitialisation requiredConnecting the diagnosis system required
all types approximately ø 35 mmNoNoYesYes
all types approximately ø 50 mmYesYesYesYes
Only for F25 : RLSapproximately ø 50 mmNo(new substitute visuals required, refer to Electronic Parts Catalog)NoYesYes
  • X5: F15, F85
  • X6: F16, F86
Sensor type/Sensor shapeWith windscreen replacement, a replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing the sensor initialization requiredConnecting the diagnosis system required
all types approximately ø 35 mmNoNoNoNo
  • 1-Series: F2x
  • 2-Series: F2x
  • 3-Series: F3x, F8x
  • 3 Series GT: F34
  • 4-Series: F3x, F8x
Sensor type/Sensor shapeWith windscreen replacement/ replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing the sensor initialization requiredConnecting the diagnosis system required
all up to 03/2014 except SBS (01)(Designation is located on the back of the sensor)approximately ø 35 mmNoNoYesYes
SBS (01)(Designation is located on the back of the sensor)approximately ø 35 mmNoNoNoNo
All as from 03/2014approximately ø 35 mmNoNoNoNo
  • 2-Series: F4x
Sensor type/Sensor shapeWith windscreen replacement, a replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing the sensor initialization requiredConnecting the diagnosis system required
all typesNoNoNoNo

BMW i:

Sensor type/Sensor shapeWith windscreen replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing the sensor initialization requiredConnecting the diagnosis system required
all types approximately ø 35 mmNoNoNoNo

BMW from the G series

Sensor type/Sensor shapeWith windscreen replacement / Replacementsensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing the sensor initialization requiredConnecting the diagnosis system required
all typesNoNoNoNo

MINI (all):

Sensor type/Sensor shapeWith windscreen replacement/ replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing the sensor initialization requiredConnecting the diagnosis system required
all types square 60 x 40 mmNoYesYesYes
all types approximately ø 35 mmNoNoNoNo

Rolls-Royce:

  • RR1
  • RR2
  • RR3
  • RR4
  • RR5
  • RR6
Sensor type/Sensor shapeWith windscreen replacement/ replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing the sensor initialization requiredConnecting the diagnosis system required
all types square 60 x 40 mmNoYesYesYes
all types approximately ø 35 mmNoNoYesYes
all types approximately ø 50 mmYesYesYesYes

Rolls-Royce:

  • RR11
  • RR12
Sensor type/Sensor shapeWith windscreen replacement/ replacement sensor requiredWhen replacing the sensor programming/encoding necessaryWhen replacing the sensor initialization requiredConnecting the diagnosis system required
all types approximately ø 35 mmNoNo

Georg Meier

BMW technician since 1996. I began my automotive journey in 1993 as an apprentice mechanic at Automag, the world's oldest BMW dealership in Munich. With years of experience and dedication, I garnered a wealth of knowledge about the intricacies of BMW and MINI vehicles. The love/hate relationship with the brand led me to found BIMMERIST where I share expertise and insights with fellow enthusiasts.

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