Central Electric Module
 

I bought a 2004 s40 1.9 . The left headlight low beam is inop. The previous owner thought it was the housing so they got an extra headlight housing. I testes the voltage going in and got .4v-5v. Tested the power from the fuse to the CEM and got batt v. Continuity from CEM was .01 ohms. I have narrowed it down to the power side of the relay within the CEM. Passenger lights and highbeams work just fine. I am considering splicing the left and right headlights together and upping the fuse by 5 to handle the increased current. I can use ohms law to estimate the current flow but bulb R can change with heat. I am just trying to pass inspection for now until I can find another CEM. If the new to me CEM is installed, must it be programmed?

on the S40 1/9s the CEM does not need to be programmed. You will find it under the drivers side dash just above the hood release. You can probably get by with a used unit - I found one for $65 and its worked fine since.

not sure why the P/O got a whole new headlight housing - if there's an issue its with the connector to the bulb - the bucket itself is all plastic.

Thank you, ive found, tested and disassembled it to see if the relays were serviceable. I found that they were not so ive been looking for new ones in scrapyards but I cant find a 2000-2004. Found a few on ebay but hated waiting. I then saw ads to reprogram them and wasnt sure if that was required for this year.

reprogramming is for the newer models, you can go with a used CEM or search for info on how to solder in your own replacement relays for the low beams

If you are handy with a solder tool then just replace the relays.

I picked up one for $35 at a salvage yard. Ill plug it in and see if it works. If not ill crack them both open and replace the faulty relays.

Replaced the CEM and my ac/blower works fine now (had been going off and on) and lights work fine. The $35 salvage yard unit works for now.

jharvey3, thanks for the confirmation. That's bound to help others with similar problems in the future. Heck, I'm a techie, and really handy with a soldering iron, and there's no way I'd want to fiddle with trying to fix one if there's a $35 replacement option! Well played!