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. | Explanation | No. | Explanation |
| 1 | Rain, light, and solar sensor | 2 | Flexible 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 shape | With windscreen replacement sensor required | When replacing the sensor/Programming/encoding necessary | When replacing the sensor/Initialisation required | Connecting the diagnosis system required |
| Condensation sensorsquare 30 x 20 mm | Yes | No | No | No |
- 5-Series: E6x
- 6-Series: E6x
- 7-Series: E6x
| Sensor type/Sensor shape | With windscreen replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing substitute visuals Programming/encoding is necessary | When replacing the sensor/substitute visuals Initialisation required | Connecting the diagnosis system required |
| all typessquare60 x 40 mm | No | Yes | – | Yes | Yes |
| RLS approximately ø 50 mm | No(new substitute visuals required, refer to Electronic Parts Catalogue) | – | No | Yes | Yes |
- X5: E70
- X6: E7x
| Sensor type/Sensor shape | With windscreen replacement, replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing substitute visualsProgramming/encoding is necessary | When replacing the sensor/substitute visualsInitialisation required | Connecting the diagnosis system required |
| RLPSS (Rain, light, and precipitation solar sensor)(Designation is located on the back of the sensor)approximately ø 50 mm | Yes | Yes | – | Yes | Yes |
| RLS (vehicle with no HUD)(Designation is located on the back of the sensor)approximately ø 50 mm | No(new substitute visuals required, refer to Electronic Parts Catalogue) | – | No | Yes | Yes |
| RLSS (vehicle with HUD)(Designation is located on the back of the sensor)approximately ø 50 mm | Yes | Yes | – | Yes | Yes |
- 1-Series: E8x
- 3-Series: E9x
- X1: E84
- X3: E83
- Z4: E89
| Sensor type/Sensor shape | With windscreen replacement, replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing the sensor initialization required | Connecting the diagnosis system required |
| all types square 60 x 40 mm | No | Yes | Yes | Yes |
- 5-Series: F1x
- 5 Series GT: F07
- 6-Series: F06, F1x
- 7-Series: F0x
- X3: F25
- X4: F26
| Sensor type/Sensor shape | With windscreen replacement, replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing substitute visualsProgramming/encoding is necessary | When replacing the sensor/substitute visualsInitialisation required | Connecting the diagnosis system required |
| all types approximately ø 35 mm | No | No | – | Yes | Yes |
| all types approximately ø 50 mm | Yes | Yes | – | Yes | Yes |
| Only for F25 : RLSapproximately ø 50 mm | No(new substitute visuals required, refer to Electronic Parts Catalog) | – | No | Yes | Yes |
- X5: F15, F85
- X6: F16, F86
| Sensor type/Sensor shape | With windscreen replacement, a replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing the sensor initialization required | Connecting the diagnosis system required |
| all types approximately ø 35 mm | No | No | No | No |
- 1-Series: F2x
- 2-Series: F2x
- 3-Series: F3x, F8x
- 3 Series GT: F34
- 4-Series: F3x, F8x
| Sensor type/Sensor shape | With windscreen replacement/ replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing the sensor initialization required | Connecting the diagnosis system required |
| all up to 03/2014 except SBS (01)(Designation is located on the back of the sensor)approximately ø 35 mm | No | No | Yes | Yes |
| SBS (01)(Designation is located on the back of the sensor)approximately ø 35 mm | No | No | No | No |
| All as from 03/2014approximately ø 35 mm | No | No | No | No |
- 2-Series: F4x
| Sensor type/Sensor shape | With windscreen replacement, a replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing the sensor initialization required | Connecting the diagnosis system required |
| all types | No | No | No | No |
BMW i:
| Sensor type/Sensor shape | With windscreen replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing the sensor initialization required | Connecting the diagnosis system required |
| all types approximately ø 35 mm | No | No | No | No |
BMW from the G series
| Sensor type/Sensor shape | With windscreen replacement / Replacementsensor required | When replacing the sensor programming/encoding necessary | When replacing the sensor initialization required | Connecting the diagnosis system required |
| all types | No | No | No | No |
MINI (all):
| Sensor type/Sensor shape | With windscreen replacement/ replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing the sensor initialization required | Connecting the diagnosis system required |
| all types square 60 x 40 mm | No | Yes | Yes | Yes |
| all types approximately ø 35 mm | No | No | No | No |
Rolls-Royce:
- RR1
- RR2
- RR3
- RR4
- RR5
- RR6
| Sensor type/Sensor shape | With windscreen replacement/ replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing the sensor initialization required | Connecting the diagnosis system required |
| all types square 60 x 40 mm | No | Yes | Yes | Yes |
| all types approximately ø 35 mm | No | No | Yes | Yes |
| all types approximately ø 50 mm | Yes | Yes | Yes | Yes |
Rolls-Royce:
- RR11
- RR12
| Sensor type/Sensor shape | With windscreen replacement/ replacement sensor required | When replacing the sensor programming/encoding necessary | When replacing the sensor initialization required | Connecting the diagnosis system required |
| all types approximately ø 35 mm | No | No |
