Mercedes-Benz C-Class W204 rain sensor retrofit

Hello. In this guide I’d like to tell you how I retrofitted rain sensor in my car.

Things you’ll need:
- Replacement rain-light sensor
- A thin screwdriver to remove old sensor
- A laptop with a diagnostic interface (e.g. OpenPort) and Vediamo with CGW_204.CBF

General information: I’ve got a 2007 Mercedes-Benz C-Class W204 1.8 Kompressor. Straight out of factory, it had light sensor (that enables headlights when it’s dark). But it didn’t have rain sensor. I heard it’s very convenient to have automatic windshield wipers so I decided to improve my car.

I started with removal of my current light sensor. It’s a very simple procedure. Here’s a good guide on how to do it: https://www.youtube.com/watch?v=CLilFckqCn8 . BTW Greetings for you Mikey! You helped me a lot with many things.

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Then I used parts catalogue to find right light-rain sensor. Not all of them match correctly! I used option codes to find right one. Most important option code is model year. Mine is 808 — as my car is model year 2008. You may be having one of these: 808, 809, 800, 801, 802, 803, 804, 805, 806. 345 is option code for rain sensor.
My factory sensor is A2048204326. For me it turned out following sensors match: A2048201285, A2048208385, A2048703426, A2048708826, A2049017801. Buying incorrect sensor may result in error appearing in instrument cluster!

Left: my factory light sensor. Right: light-rain sensor from facelifted W204. Buying it was a mistake. I returned it.

I first bought incorrect sensor (model for facelifted cars). After installing it, I had “AUTO light inoperative” error. It turned out I made a mistake and had to buy another one. After installing right sensor… no errors, no changes at all. Spraying window cleaner onto windshield resulted in no automatic wiping.

Right sensor installed in place

It turns out coding is necessary. I used Vediamo for it. It may be possible if you’ve got DAS. Steps:

1. Make sure you’ve got CGW_204.CBF in your C:\ProgramData\Vediamo\VediamoData. If you don’t have and you’ve got Xentry, you can copy the file from C:\Program Files (x86)\Mercedes-Benz\DAS\comdat\pkw\cbf.

2. Open Vediamo Ecoute. Select CGW_204.

3. Initiate ECU Contact. If it fails, you may have to change connection mode. In the ECUs folder click right on the CGW_204, select Properties. In Connection field, select one that finishes with 500 instead of 125.

4. Open Variant Coding menu.

5. Perform coding change in VCD_02_global_variant_coding. Change 345 Regensensor to available. After selecting, click ECU coding. When it succeeds, close Vediamo. Take car key off and put it back.

6. Test wipers. Turn them on by selecting slowest wiper mode. The wipers shouldn’t work right away. Spray some water onto the windshield. The wipers should do the job.

7. Voila! If you’ve got some questions, let me know. I’ll try to help