Thread: Front light problem - 2017 L494

Hi Everyone,

I am hoping someone can help me work out what is going on with the front lights on my L494 V6 Diesel. (after owning a P38A for twenty years I thought I had a decent fault solving ability, but this has me stumped so far, and searching forums from all over have not shed any light on the issue).

Last week I noticed that the turn signal (blinker) was flashing and clicking quickly (dash indicator only), both directions.....looked up why, and suggested faulty light......checked, and they all seem to be working. They flash at normal (slower) speed on the dash when hazard lights are on.

I connected up my icarsoft reader, and had 2 faults under the BECM - BC103C-87 (Left Headlamp Control - Permanent) and BC103D-87 (Right Headlamp Control - Permanent). I tried to clear these codes, but as it says....they are permanent.

Reading on many forums I read of corroded earth points behind the front wheel arch linings.....I removed both linings, and to my disappointment the earth studs and connections are clean, tight, and each have <0.2 ohms to chassis. I undid each one, and checked the cables etc....but it made no difference, and everything checked out fine.

I have now focused of the front lights, and found that the Xenon headlights both high and low beams work fine. There are some turn signal indicators working on the edge of each headlight, but I don't think that is the full compliment (as the amber reflections from signs etc. seems duller at night than it used to). The DRL and cornering lamps do not seem to work either, I would always notice them in a shop window reflection etc.
I have made a diagram to explain which parts of both headlights are not functioning.

Faulty headlights.jpg

Today I tried disconnecting each headlight, and seeing if there were any changes, but it made no difference. I'm trying to figure out if it is a communication issue from the CJB to the headlights, or faulty LED control modules on each headlight......the fact that both are behaving the same way makes me think the issue is to do with the LED control or drive for both lights - Unlikely both headlights have failed together. I can't seem to locate any fuse that relates to the LED headlight control system - Fuse 14 (10A - Red) in the luggage compartment says it does headlights, blind spot, reversing camera etc....Camera and Blindspot are working fine.

I would appreciate any ideas, or thigs to try, as I'm at a loss at the moment the next steps.

Thank for reading, Cheers,
Bruce

Hi Graeme,

Thanks for the suggestion. I'll look into it more. When I have a chance I want to take a headlight out, and hook it up manually to the various 12v inputs, and see if it all works on the bench. My L494 is a 2017 build with a 2018 plate, so some diagrams show the headlight with a separate LED control module underneath, as well as the ballast module for the Xenon lights, some only show a ballast underneath, and an LED control PCB inside the headlight housing - I've found some details of repair on those PCB's when the 5v Regulator blows, but again the fact that both lights are behaving the same way it makes me think it could be a comms issue either to the BECM or the CJB. The next logical step I can see is removing the headlights, and bench testing them to see if they are fully functional, or not. I just downloaded the last version of RAVE, and will go through the Electrical Manual to work out headlight pinouts. I won't have time to pull out a headlight until sometime next week.

Thanks again,
Bruce

Thanks for the link to headlight PCB.....That was the same one I was researching.