So this vehicle last night decided to start turning on/off the headlights randomly. This is not happening rapidly, instead the right one would stay on for a few seconds then turn off for around 30 seconds. The left one would stay on for around 20 seconds then turn off for around 10. This is of course give or take a few seconds either way. Today the driver side is not operating at all and the left one will stay on for a couple minutes after the car is started then start acting up and eventually turning off all together.

I've done some digging around and after looking at the wiring diagram am thinking that it is the Central Electronic Module.

My question is are there any relay's on it that could cause this problem or am I possibly looking at having to replace the whole module? If it is the module does anyone know the correct part number so I don't order the wrong one?

I just want to make sure before I start sending money out the door.

 

You need to inspect the wiring inside the headlights and along the body. What you are describing sounds like a wiring problem. I've never had a lighting module go bad so start with the simple stuff.

You should also visit someone who has diagnostic software to see if there are any stored codes, etc.

What you are doing is shooting in the dark unless you use the diagnostics.

 

I'll check to see if it's throwing any codes. I was thinking wiring until I saw that the only place that both headlights tied into was the CEM and upstream from that at the switch. Even the ground strap is located in the wheel wells for each respective side. Since both the driver side and passenger side started acting funky at the same time, I decided that the wiring is likely not the case. I did check the wiring harness at each light to make sure and they are both clean. Also did some wiggle testing while it was on to see if anything showed differently and it still acted the same.

 

I had a similar thing happen with my headlights. It turned out that one of the two male pins in the headlight had bent from the last time I had replaced the bulbs. I guess I was not careful enough in making sure that the pins were completely straight before plugging the replacement lights in.

 

if I had an issue with one single headlight I could see wiring being a possible cause. The problem is this is happening to both headlights and it started at the exact same time.

so I went and grabbed a cem from a 2007 Volvo V60 at the local junkyard. Got it installed and no start. For my research this was supposed to be a compatible unit. Not sure if the cem have to be programmed to a specific vehicle or if the cem that I got is just a dud. Any input on that?

 

yes the newer CEMs need to be paired to your car by a dealer. Older CEMs (like my 00 S40) do not need to be paired.

 

Thanks for the input. Something else I'll have to research now.