False "Bulb Failure Low Beam" Message - 2004 XC90 T5

joelq · Post by **joelq** » 19 Jan 2012, 16:16

Hi all -

I have a 2004 XC90 T5 with standard halogens and ~142K miles. I am getting the message "Bulb Failure Low Beam", except that both low beams are working just fine. Jiggled all connections, replaced the bulbs, and even swapped headlight assemblies with another known working set, and still get the message.

Any thoughts on where else to look?

Thanks!

Post by **jimmy57** » 19 Jan 2012, 20:26

on the CEM under the left front dash there are black rectangular things that are the bulb failure detection shunts. Push on all those and see if the message is gone.

joelq · Post by **joelq** » 20 Jan 2012, 05:56

jimmy57 wrote:on the CEM under the left front dash there are black rectangular things that are the bulb failure detection shunts. Push on all those and see if the message is gone.

Thanks so much for your reply! I've got follow-up questions:

- is this accessible without having to take the dash apart?
- are these "shunts" circuit breakers that trip and I'm just looking to reset them?

Thanks!

joelq · Post by **joelq** » 20 Jan 2012, 12:10

OK - so I went looking under the driver's side dash today to see if I could see something that resembled what you were describing, and saw this:

Is this the CEM? For the black rectangular things that you mention, are they the squarish looking ones in the front, or the skinny fin-looking ones in the back-left?

joelq · Post by **joelq** » 15 Feb 2012, 08:59

Bump. I'm still having the problem. Anyone else have any insight?

joelq · Post by **joelq** » 15 Feb 2012, 11:18

Quick update - through other threads, I figured out that the shunts are the skinny fin-looking things, and that the lowest (in the picture) shunt controls the low beams. I confirmed this by removing the resistor and my lights stopped working altogether.

Just as a quick test, I swapped that resistor with the one right above it (confirmed same part number) and that didn't do anything. Does that confirm that the problem isn't the resistor? Unless both resistors are bad, which I would doubt.

Any suggestions? Thanks!

Post by **gshadow325** » 22 Feb 2012, 05:03

http://xcforums.com/topic/393-xc90-diy- ... #entry1266

becha coffee this will fix it...simple

joelq · Post by **joelq** » 22 Feb 2012, 06:53

gshadow325 wrote:http://xcforums.com/topic/393-xc90-diy- ... #entry1266

becha coffee this will fix it...simple

Thanks, gshadow325! Looks simple enough - but if I'm understanding this correctly, I'm basically disabling the bulb failure detection, right? Although at this point, I just want to get rid of that yellow triangle on my dashboard!

Thanks!

Post by **gshadow325** » 22 Feb 2012, 07:56

yes it will, simple fix. all this mod does is create a higher resistance for the CEM. raises it from 10ohms to 13 or 14ohms, thats it.

joelq · Post by **joelq** » 22 Feb 2012, 16:44

Well, I tried the drill fix this afternoon, and the message is still coming up. I'm starting to think I have a bad CEM.

Any other suggestions?