This one has me stumped I have been pounding my brain senseless trying to locate what powers the center brake light.

I have been studying the wiring diagram so give you what I was able to find out so far. Via the diagram the center light (10/19) gets its signal from the CEM (4/56) through the roof harness (54/13). So I decided to take a look at the relays and shunts for the CEM and for the life of me cannot find what functions the center brake light (10/19).

All lights work properly except the center brake light when I step on the brake the bulbs in the tail lights get brighter and I can hear the relay in the REM as well. I also went for a long shot and swapped out every fuse and relay in the REM hoping to find it that way. Then after checking the wiring diagram I see that the harness goes to the CEM and not the REM but for the life of me cannot figure out what relay or fuse it is that would power it, and I am not sure what to check at this point.



Link above if for the diagram , if you see something I don't or know of what I should check please advise.

 

link didn't work so here is the list of diagrams ...I got a 2004 s60


http://www.volvowiringdiagrams.com/?...ing%20Diagrams

 

There are no external relays or shunts for the third brake light.

If the third brake light has good ground and power, the third brake light should be replaced.

If the third brake light has good ground but no power, verify continuity between 4/56:B5 and 10/19:1. If there is continuity, the CEM needs to be replaced.

 

Hi ES6T thanks for chiming in, thats what I was thinking as I seee on the diagram it makes its connection though the CEM sending a signal to the 3rd light and the REM at the same time via a different wire.

I will verify continuity between 4/56:B5 and 10/19:1 and take it from there, Super thanks !!

If the CEM need to be replaced does that have to be vin matched or programmed?

 

Yeah the CEM is programmed to the car. Check with xemodex.com to see if they have rebuild options available.

 

Volvo Wiring Diagrams

 

I went ahead and talked to Xemodex and they told me to send in the CEM and that they would test it for faults before doing a repair. So I pulled the CEM out and also pulled a good one out of my sons wrecked S60 sent then both units. They say because the part numbers were different that the CEM we sent them cannot be re-programmed and that they did find faults in the CEM we sent them. so now instead of a 300.00 software transfer they say we need to buy the whole unit from them 654.00. They claim that the DTC stored faults were: -EE-Prom Failure, -8D02- Ignition lamp & High mounted Stop (brake)lamps signal too high/signal missing, -6C48- Transponder type faulty signal.

So I was under the assumption that they found faults in the CEM that related to the 3rd light being out and we went ahead with the new cem though them. Got the CEM yesterday installed it and its exactly the same issue nothing has changed.

Been trying to research this issue and have found that I am not the only one that has had issues and have found a thread on people running a jumper wire from the trailer lights to the 3rd brake light , although I would prefer to fix it the correct way but I am not sure where to go from here.

Here is a link to the info I found, its not much besides the same issue with a work around. Upper Third Brake light not working failure

 

The circuit is very straight forward. If there is no power to 10/19:1 and there is continuity through 4/56:B5 to 10/19:1 there are no other possibilities besides the CEM. Obviously the brake light switch is working since the other brake lights work.

 

Yippee, I got it....the CEM was good this time I was able to get voltage though the CEM and now my light works.


Now I got a new issue, but I'll start another post on that after I do some more investigating.

Thanks again ES6T