Tail Lights and License Plate Lights Out
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    1. #1
      Global Moderator MyNameIdeasWereTaken's Avatar
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      Tail Lights and License Plate Lights Out

      Tail lights and license plate lights are out.
      Brake lights, rear fog light, turn signals, reverse light, hatch release, window defroster, and rear wiper all work.

      Ran a test wire directly to the tail lights from a 12v socket and they all lit up, so bulbs and grounds are fine.

      Sometimes when first turning the lights on, they illuminate very dim for about 2 seconds and then go out. Sometimes they don't come on at all.

      Fuses for associated items look good. There is not a fuse specifically listed for the tail lights. However, other Volvo models mention a relay for the tail lights and licence plate lights.

      My best guess on a 2006 is F58 "Right high beam; auxiliary lights relay; 7.5A"
      I'm thinking it could be a bad relay. Where is this relay located?
      The wiring diagram clearly shows that it is not part of the CEM.



      If it's not the relay, any other ideas for what it could be? I'm about ready to run a new power wire to another ignition power source if I can't get this figured out... Can't drive without tail lights.

      Edit: Just noticed that the city lights and parking lights are also out. So it's definitely something associated with all of the auxiliary lights.

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    3. #2
      Member thefisch33's Avatar
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      Maybe related to the headlight switch? In mode 0 since my DRLs are disabled it does exactly what you describe. Everything but tail lights and license plate lights
      2010 s40 T5 AWD M66 a tribute to Heico's ODIN HS4

    4. #3
      Junior Member Jirv0id's Avatar
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      Is it possible that the slight glow is the LCM testing then it noticed a major failure and disables the lights?
      2007 V50 T5 AWD M66 ~ Custom machined weighted shiftknob powdercoated wrinkle polstarblue, Custom pod filter intake, Muffler delete, 18" Pegasus IPD Reps, EBC redstuff pads, EBC blank rotors.

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    6. #4
      Global Moderator MyNameIdeasWereTaken's Avatar
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      Quote Originally Posted by thefisch33 View Post
      Maybe related to the headlight switch? In mode 0 since my DRLs are disabled it does exactly what you describe. Everything but tail lights and license plate lights
      DRLs are not disabled on this car. It does it in the On position and parking light position. Low beams are still on. There is no power going to any of the auxiliary lights.

      Quote Originally Posted by Jirv0id View Post
      Is it possible that the slight glow is the LCM testing then it noticed a major failure and disables the lights?
      Entirely possible. Which still leads me to the problem of tracking down where the wires go. I know that at the bulb sockets for tail lights, license plate lights, city lights, and parking lights, there is no power. The fuse for the auxiliary lights relay is good and has power. So the problem is somewhere after that.
      The fact that all of these lights decided to go out at once leads me to believe it's something that controls all of them. The relay would make sense.

      I tore apart the dash and could not find any relay between the A pillar and center console. Nothing on the other side of the firewall or in the wheel well either. The wiring diagram is really no help... But it's definitely not part of the CEM (according to the picture) because the relays that are part of the CEM are clearly listed.

      By yesterday afternoon, I gave up. I can live without city and parking lights, pulled those bulbs on past cars anyway. The license plate lights are now wired into my tail lights and the taillights are getting their power from an ignition power source. I'll be wiring up an indicator light in the cabin to signal when the lights are on, so I have a visual notification if they blow a fuse or go out again.

    7. #5
      Member theshadow27's Avatar
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      Are you getting a bulb failure notification? All of those lights are PWM controlled by the CEM and monitored for under/over current. There is no direct fuse, it's a "digital fuse" that, like the headlights, if the circuit draws too much current it cuts it off.

      I would check VIDA as it can report on the status of the circuits individually. If a whole bunch are bad, and it's getting worse, it could be something with your CEM (e.g. heater core leak, etc).

      edit: There are a bunch of relays in the CEM which are not listed... but none of are involved with tail lights or license plate - all the PWM lights (except for headlights) run through F4/F18 and the main system relay.
      Last edited by theshadow27; 12-03-2018 at 11:47 AM.
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    8. #6
      Global Moderator MyNameIdeasWereTaken's Avatar
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      Quote Originally Posted by theshadow27 View Post
      Are you getting a bulb failure notification? All of those lights are PWM controlled by the CEM and monitored for under/over current. There is no direct fuse, it's a "digital fuse" that, like the headlights, if the circuit draws too much current it cuts it off.

      I would check VIDA as it can report on the status of the circuits individually. If a whole bunch are bad, and it's getting worse, it could be something with your CEM (e.g. heater core leak, etc).

      edit: There are a bunch of relays in the CEM which are not listed... but none of are involved with tail lights or license plate - all the PWM lights (except for headlights) run through F4/F18 and the main system relay.
      No bulb failure warning and no codes. All circuits are reported as good. Just no power at the bulb sockets when tested with a multimeter.
      Are you sure these would give some sort of a message? I've had city light, tail lights, and license plate light bulbs burn out on many P1 Volvos and never got any notification or read any errors about it.
      I've only ever gotten a dash message or seen a warning in VIDA when the low beams or brake lights go out.

      One of the first things I did was pull the CEM and inspect it. This one is only a few months old and still appears fine.

      I think all the internal CEM relays are listed on the wiring diagram. But the one that is associated with "Auxiliary lighting" is not listed as being part of the CEM, which is why I'm confused on where it is. Since the S60 and XC90 lump tail lights and license plate lights into the same category as "auxiliary lighting," I'm thinking the P1s might as well.

    9. #7
      So just my .02 here:

      Did you unplug them both then plug either side in testing to see if it's either side of the harness that's good/bad?
      With the load cut in half it should alter the behavior of the relay if it is in fact a relay issue.

      I also would check the harness on both sides for a grounding issue by checking un unpowered 12v line to ground and pull the carpet down in the trunk to check the grounds as well if there isn't a 12v going to an unintended ground issue.
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    10. #8
      Member AutoGeek's Avatar
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      It sounds like you may have a weird short somewhere. I had similar happen when I did my headliner. The interior lights wouldn't come on when I pressed the appropriate switch but would kind of come on when other switches were turned on. It turned out to be a pinched wire under one of the headliner brackets. The system apparently finds sneak paths.

      I looked at the wire diagrams but no smoking gun. I suspect it may be finding a such a sneak path maybe through the CEM.
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    11. #9
      Global Moderator MyNameIdeasWereTaken's Avatar
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      Quote Originally Posted by avenger09123 View Post
      Did you unplug them both then plug either side in testing to see if it's either side of the harness that's good/bad?
      With the load cut in half it should alter the behavior of the relay if it is in fact a relay issue.

      I also would check the harness on both sides for a grounding issue by checking un unpowered 12v line to ground and pull the carpet down in the trunk to check the grounds as well if there isn't a 12v going to an unintended ground issue.
      I stripped the trunk area and the wiring visually looks good. It's definitely not a ground issue because supplying an external power source makes the lights illuminate no problem with their current grounds. If I'm not mistaken, all of the lights in each light assembly share the same ground and the other lights are working fine.

      I did not try unplugging just one side.

      But again, the fact that the front and rear auxiliary lights went out at the same time suggests that it's something that controls all of those lights. If it was an issue with just one taillight, it shouldn't effect the city lights, parking lights, and license plate lights.

      Quote Originally Posted by AutoGeek View Post
      It sounds like you may have a weird short somewhere.

      I looked at the wire diagrams but no smoking gun. I suspect it may be finding a such a sneak path maybe through the CEM.
      It's possible. The problem is, short of tearing out the entire interior and following the wires, I don't know the exact route things take.
      Logically, I think it has to be something between the fuse and the relay, since the fuse has power and all the lights coming off of the auxiliary lights relay do not have power.
      But I still don't know where that relay is... I spoke with a Volvo tech and they don't know either, since it's obviously not a common problem. They looked at the wiring diagram and confirmed this relay is not part of the CEM.

      At this point, my re-wired fix is working fine, so I'm content. Just another unsolved electrical mystery with this car.
      Thanks to everyone for the suggestions and help!

    12. #10
      Member theshadow27's Avatar
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      I am sure that there is no relay associated with those lights... Just verified it in the car: with it off, press the yellow button on the remote a few times. Lights turn on and off completely silently. Compare to the extremely audible click with the when you activate the high beam stalk while the key is out.

      Quote Originally Posted by MyNameIdeasWereTaken View Post
      Are you sure these would give some sort of a message? I've had city light, tail lights, and license plate light bulbs burn out on many P1 Volvos and never got any notification or read any errors about it.
      Single-bulb circuits (low beam, brake lights, turn signals) have a DIM message on failure (open circuit), and a silent (VIDA-only) code on short-circuit. Multi-bulb circuits (running lights, city lights, and license plate lights) don't detect failure, but do store a silent code on short circuit. No message on dash, but they do store a code (signal out of range low).

      Quote Originally Posted by MyNameIdeasWereTaken View Post
      I think all the internal CEM relays are listed on the wiring diagram. But the one that is associated with "Auxiliary lighting" is not listed as being part of the CEM, which is why I'm confused on where it is. Since the S60 and XC90 lump tail lights and license plate lights into the same category as "auxiliary lighting," I'm thinking the P1s might as well.
      "Auxiliary Lighting Accessory" was an factory option, the power takeoff (same fuse / enable as the low beam) is to activate it's relay, see:
      https://forums.swedespeed.com/showth...rt-Numbers-Etc

      Not related to the tail/city lights.

      Quote Originally Posted by MyNameIdeasWereTaken View Post
      I stripped the trunk area and the wiring visually looks good. It's definitely not a ground issue because supplying an external power source makes the lights illuminate no problem with their current grounds. If I'm not mistaken, all of the lights in each light assembly share the same ground and the other lights are working fine.

      At this point, my re-wired fix is working fine, so I'm content. Just another unsolved electrical mystery with this car.
      Thanks to everyone for the suggestions and help!
      Very very strange. I guess if you've fixed it and are happy, don't go looking for trouble. You're right, it could be anywhere, but my suspicion is somewhere related to the license plate/trunk harness - those wires fray quite often inside of the rubber tube thing.
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    13. #11
      Member EngTech's Avatar
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      As You Know ~/~

      Did You ever Clean and Carefully re-check all Alignments on All the CEM Connections ?
      As those can get very Finicky . . PINS all in right Spots & Not Sharing as too slight mismatch , Best I Got !

      Just a Wiff to much electrical Grease can be Bad also ( Block or allow Path Crossing )
      Last edited by EngTech; 12-09-2018 at 02:44 PM.
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    14. #12
      Member EngTech's Avatar
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      I also would say Google the Differences Sorry to Others on SS I don't Wish to Confuse anyone : Between : Dielectric Grease VS Regular Grease . .

      Also :
      NO-OX-ID electrical contact lubricant (electrical contact grease) is an electrically conductive grease . .

      Also :
      Dielectric grease is a non-conductive grease. Because it is non-conductive it does not enhance the flow of electrical current. Electrical conductors should not be coated with dielectric grease prior to being mated. However, dielectric grease is often applied to electrical connectors, particularly ones which contain rubber gaskets, as a way to provide a non-conductive lubricant and sealer for the rubber portions of the connector.

      So too Much of Good Thing could Hamper Low Voltage Circuits ( On Contact Points Areas ) There are also Greases that have Metals in them which would cause - Path Transfer . .
      It's also Plausible - that such Grease could be Accidental Transferred . .

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    15. #13
      Global Moderator MyNameIdeasWereTaken's Avatar
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      Yep, checking and cleaning the CEM connection points was part of my initial search to find the problem with this.

    16. #14
      Member EngTech's Avatar
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      Here's a Good Example of Conductive Grease To Enhance the Electrical Connection between conductors, I use a conductive grease like BURNDY PENETROX.
      Yep and Wikipedia is Better the Google




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    17. #15
      Junior Member JomamaAK's Avatar
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      I've got something similar but not exactly the same going on, and was also perplexed by the lack of fuses for the rear tail light/parking lights.

      On my DS tail light/parking light combo, I just noticed the inner of the two bulbs was out. I went to replace it but a new bulb didn't fix the issue. I then swapped the presumably burned out bulb into the other tail light socket and it works.

      So the issue appears to be with the socket or wiring, which is attached to the plastic plate which also has the reverse light & signal(?) sockets mounted to it along with the 2x tail-lights sockets.

      If it was the wiring or fuse I'd think it would affect both sockets? Only one of mine isn't working.

      Anyone else encounter this? Is there really no fuse's for the tail lights?

      ~Cheers!
      Last edited by JomamaAK; 12-02-2019 at 07:20 PM.
      2005 V50 T5 AWD Auto

    18. #16
      Quote Originally Posted by JomamaAK View Post
      I've got something similar but not exactly the same going on, and was also perplexed by the lack of fuses for the rear tail light/parking lights.

      On my DS tail light/parking light combo, I just noticed the inner of the two bulbs was out. I went to replace it but a new bulb didn't fix the issue. I then swapped the presumably burned out bulb into the other tail light socket and it works.

      So the issue appears to be with the socket or wiring, which is attached to the plastic plate which also has the reverse light & signal(?) sockets mounted to it along with the 2x tail-lights sockets.

      If it was the wiring or fuse I'd think it would affect both sockets? Only one of mine isn't working.

      Anyone else encounter this? Is there really no fuse's for the tail lights?

      ~Cheers!
      Yeah, often times people put the incorrect wattage bulbs in their light sockets, and even though they only vary by 2.5w and 3 models fit, the extra heat is enough to flex the connector or the plastic and cause it to lose touch with the bottom of the bulb. Pop it out and bend the connections back up a bit and then retry, should work. Then go get the correct bulbs for the socket.
      Last edited by avenger09123; 12-02-2019 at 10:49 PM.
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    19. #17
      Junior Member JomamaAK's Avatar
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      Quote Originally Posted by avenger09123 View Post
      Yeah, often times people put the incorrect wattage bulbs in their light sockets, and even though they only vary by 2.5w and 3 models fit, the extra heat is enough to flex the connector or the plastic and cause it to lose touch with the bottom of the bulb. Pop it out and bend the connections back up a bit and then retry, should work. Then go get the correct bulbs for the socket.
      Awesome tip, I will definitely try that. Will double check the bulb types too. Thanks!
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    20. #18
      Global Moderator tmtalpey's Avatar
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      Quote Originally Posted by JomamaAK View Post
      Is there really no fuse's for the tail lights?
      And OBTW, that's mostly correct. Many of the lights are energized directly from the CEM via PWM voltage. The CEM drivers provide their own overcurrent protection. Good connections at the bulbs are vital as there is no "bulb out" indication thrown for the license plate lighting.
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