2007 volvo xc90 hazard light issue
 

I've referred to this forum as a guest MANY times and gained useful information. This is my first post and I'm at my wit's end. Bought a 2007 Volvo XC90 AWD with a 3.2 a few weeks ago. Vehicle had minor front end damage when bought, but was able to run and drive perfectly. After driving it for about 3 weeks I purchased a pair of after market halogen head lights and installed them with a new front bumper cover. I used the wiring harnesses that came with the new lights instead of the originals, didn't really think much about it, it was just easier to use the harness that came with the head lights. As soon as the new head lights were installed the flashers came right on as as we started the vehicle to check all the bulbs. I initially thought, "ok, I somehow bumped the flasher switch, kind of weird but...". I reached up and turned them off, no problem. The very next time the vehicle was started the same thing happened, and the next, and the next, etc. Eventually, I was not able to turn them off by hitting the hazard switch. Hazards remained on and flashing, key in, key out, engine running, not running...nothing would stop them from flashing except disconnecting the battery. Reconnect the battery and within 30 seconds flashers are activated and won't turn off again. Let it sit over night, did the hard reset with the battery cables, changed the battery...nothing worked. Hard code stored in the CEM, 8F05 "Hazard Light Switch Activated Too Long". Yeah, no kidding! I was not able to clear the code with my Autel scanner, nor was my local indy shop who has a better scanner. Also, as a side note, radio lights also diminished to the point of almost not being able to see them, after installing the new head lights. Finally gave in and took it to the Volvo dealer. They called with GREAT news! It's the switch, they said. They were able to clear the code and ordered me a new switch (even thought my indy guy already told me the switch was fine). New switch came in, they installed it, hit the hazard switch and it worked for exactly three tests. Code came right back in the CEM (hazard switch activated too long) and hazard lights won't turn on, but at least they are not flashing all the time! They say they have NO IDEA what to do with it. They've never seen anything like it. Fast forward about 3 weeks, vehicle runs and drives beautiful. Still no flashers. A couple of days ago I was stopped with my RH blinker on. I turned off the ignition with the blinker still on and when I got back in the vehicle and started it the flashers came on. I reached up and tapped the switch and they turned off. PHEW! Hit the switch again to see if by some miracle they had "cured" themselves, no luck, they won't turn back on. Well, today the hazard lights are starting to come back on by themselves and won't turn off unless I disconnect the battery. Oh....dealer said they only thing they could think of is it's a faulty CEM. Tried to sell me a new CEM and programming, but with no guarantee of it working. I decided to send the CEM to Xemodex in Canada. They tested the CEM and cleared the code about hazard switch being activated too long, sent it back to me saying nothing wrong with CEM. Installed it back in the car, hit the hazard switch, nothing. Code stored back in CEM, won't clear. I'm literally about to pull my hair out right now. I own a repair shop and sell Volvos. I've seen a lot of their little quirks and always been able to fix it myself by coming to this forum or reaching out to my indy shop who has more sophisticated diagnostic tools than I do, and I have never seen anything like this. Oh, just one more tid bit of information.....I disconnected the radio because I wanted to replace it with one out of an identical vehicle that I have in my parts inventory, reached up and hit the hazard switch and it worked! On, off, on, off, on, off....and done. Worked for exactly three times before failing. At least now I do have radio lights back, but I would for sure like to figure out why these hazard lights are not working, and then at random times come on and and won't turn off until the battery is disconnected. At least at this point I CAN get them to turn off by disconnecting the battery, but I have a feeling it's just a matter of time before they come on and stay on, just like when I first started having this problem. What can anyone out there tell me about this Infotainment Control Module, the fiber optic loop and the MOST system? I am wondering if any of these three things could be causing my issue.

It sounds like there's a short within the lamps or harness/connectors that's creating a current path like a reverse feed to the hazards (effectively bypassing the switch). What happens when you pull the fuse for the hazards? What happens when you pull the fuse or disconnect the headlamps at the connector?

Don't hold me to this, my brain is a little foggy after trying so many things, but I don't believe there is a dedicated fuse for the hazard switch. I will check the owner's manual on that. I have not tried disconnecting the headlamps at the connector, but that is on my list of things to try next. Also, FYI, after this problem started I did remove the after market wiring harnesses for the headlamps and install the original OEM harnesses. That did not resolve my issue. Thank you very much for the quick reply - I will be revisiting the issue and try your suggestions and report back.

Following up on this issue I am having with my XC90. I tried everything mt6127 suggested with no positive results. Took it to a diagnostic shop and left it for about two weeks. During this time they tested it daily and under different circumstances. What they came back with was that all codes would clear and hazard lights would work as they should first thing in the morning when it was still cold out, and before the module had a chance to heat up. They were able to get everything to work right, also, with the AC cranked up full blast on the lower (feet) setting. In other words, cooling in the general vicinity of the CEM. I contacted Xemodex again and shared this information with them. They suggested that I send it back a second time (remember, I sent it to them once and they said there was nothing wrong with it) and they would transfer my programming to one of their remanufactured CEM modules. I installed the module today, codes returned right away, flashers coming on and off by themselves....in other words, no change whatsoever. The module came back with the following "WATER PENETRATION/CORROSION AT PCB." To say I am disappointed is a huge understatement. I'm so far in at this point that I hate to give up, but what the hec am I (and everyone else) missing here?

UPDATE: Long story short.....it was a bad CEM. Even though I had sent it to Xemodex for repair (once) and replacement (once) it totally WAS the CEM. I took the extreme measure of installing the CEM into another vehicle (not able to start said vehicle obviously, but it would work the flashers and DID set the code that I was having a problem with), so I was able to recreate the issue in a completely different vehicle. Called Xemodex and argued with them for about an hour on the phone. They said impossible, because they sent me a remanufactured CEM the second time. After arguing and explaining my experiment about putting the faulty CEM into another vehicle, they finally agreed to send me another CEM and......PROBLEM SOLVED!! Moral of the story - trust your gut and when it comes to funky electrical issues with these Volvos, it usually is the CEM.