How I fixed Automatic Headlight Control error in my 2016 Skoda Octavia

Whatever posts that I found, blamed the faulty rain and light sensor but it is always the little things that matter.

BHPian vaibhavyagnik recently shared this with other enthusiasts.

Problem statement:

I bought a used 2016 Skoda Octavia 2.0 TDI DSG about 1.5 years ago. Ever since I bought the car, if I put the headlight switch to Auto, I would get an error on the MFD and infotainment - Fault: Automatic Headlight control.

The headlights would light up even in broad daylight. If I put the wipers in Intermittent mode, they would start and keep wiping even if the windscreen was bone dry. I knew about this fault before I bought the car. I raised this concern to Skoda A.S.S during the paid pre-purchase inspection that I got done on the car. Skoda A.S.S said it was due to aftermarket HID and LED bulbs that the previous owner had installed in the car.

Troubleshooting:

I believed what Skoda A.S.S told me. After I purchased the car, I decided I would revert to the factory halogen setup. I even tried replacing both the low beam HIDs with H7 halogen bulbs, but even then, I would get an Automatic headlight fault if the switch was on Auto.

I then got myself OBDeleven to look at the actual error that the car was throwing. The error was "Rain/Light recognition sensor No communication" Fault code U10F600.

After looking at the error, I searched on the internet but I could hardly find anyone who had an error similar to mine. But I got a hint on obdeleven forums, that it could be a faulty sensor. I again approached Skoda A.S.S and asked them if it could be that the rain and light sensor was faulty. Skoda A.S.S again said that the fault was due to the aftermarket headlight bulbs. I knew that either they were not interested in investigating the fault or they did not know what was going on. I had to solve the problem myself.

The error stated, that the Central electrics module or the BCM was not able to communicate with the rain and light sensor. The possible problems could be:

• Faulty rain and light sensor
• Blown fuse to rain and light sensor
• Cable not plugged in either at the rain and light sensor or the BCM end
• The cable itself is damaged

I saw some YouTube videos on how to get to the Rain and light sensor. It involved removing the IRVM. I removed the IRVM and inspected the rain and light sensor connection. The cable itself had 3 wires and the connector seemed to be plugged in securely.

The wiring loom for the rain and light sensor has 3 wires. Pin 1 (Red and white) for 12VDC, Pin 2 (Brown) for earth and Pin 3 (purple and white) for LIN communication (Communication with the BCM).

I then proceeded to check the +12V and ground using a multimeter. Pin 1 was receiving 12VDC with respect to ground. Hence a blown fuse was ruled out. I was getting continuity between the ground wire and the door hinge. Hence ground was also ok.

In order to check the continuity of the wire between the rain and light sensor and the BCM, I would have to remove the wire from the BCM end. According to the wiring diagram, the wire from the rain and light sensor is connected to the 28th pin of connector C on BCM.

Accessing the BCM is tricky because it sits behind the fuse box behind the glove box. In order to access the C plug, I had to remove the trim on the side of the glove box and the trim on the passenger side running board. I do not have photos or videos, but I used this video as a reference. Although the car in the video is an LHD, the location of the BCM is the same. But since our cars are RHD, the BCM is located on the passenger side for RHD cars.

The multimeter probes were too short for measuring the continuity of the wire between the rain sensor and BCM. So, I inserted a pin on pin 28 of BCM, connected a speaker wire to the pin by twisting it onto the pin and measured the continuity of the wire. I did not get continuity. This indicated that there was a break somewhere in the wire and this was the reason why there was a No communication fault.

Tracing the cable and finding the break would have been difficult since the wire is part of a larger cable loom and it seems to go above the headliner. Hence I decided it was wise to leave the wire untouched.

I did not have the pins that go inside the BCM plug and the rain and light sensor plug so I could not make a new wire altogether. So, I snipped the original wire about 2 inches from both ends of the plug. I used the long speaker wire to bridge both the snipped ends. I covered both junctions with heat-shrink to secure both junctions and avoid shorting.

I tidied up the wire using lots of cable ties after tucking it above the headliner and through the passenger side A-pillar. I installed back all the trims. Finally, it was the moment of truth.

I put the headlight switch to Auto and I did not receive any fault on the MFD. I put the wiper stalk in an intermittent position, it wiped once and did not wipe anymore. I then sprayed some water on the rain sensor and the wipers started wiping. I covered the rain and light sensor with a thick cloth and the lights came on.

Learnings

The primary reason for writing this DIY is because I could not find the error that I was facing, even after a lot of googling. I hope that someone who is facing the same error on their VW cars stumbles on this thread. Whatever posts that I have found, blamed it on the faulty rain and light sensor. I too, was of the opinion that the sensor would be bad, because why would a cable break, specially when 12V and ground cables were OK.

Initially, I even purchased 1 used sensor off eBay of the same part number which did not work and then I purchased a new rain light and humidity sensor of a different part number which also did not work. It was only then that I decided to test the wire before throwing more money at parts. I was fortunate that the sensors themselves were not very costly (30$ each) and eBay has a good return policy, but I did have to ship the sensors back which did cost me about 550 Rs each time via India Post.

In hindsight, I should have checked the wires first. Given the fact that a bad sensor is a higher possibility and the difficulty of reaching the BCM, I foolishly decided to replace the sensors first.

It is always the little things.

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