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Chevy TrailBlazer Headlight Questions



  • fj4072fj4072 Posts: 29
    Try cleaning the heck out of the contacts in the fuse box AND the relays. This is what worked for me to solve this same problem, while still using the old relay. But I have a new relay in my glovebox just in case it ever really does go out.
  • I decided to replac the Airfilter & Plumbing with K&N filter and left the air cleaner bonnet off. The airfilter is exposed and may need to be cleaned more frequently. But its easy with K&N filter. The air inlet plumbing was replaced with a new tube that did not open to the AC bonnet so all air is filtered... :shades:
  • i have a 04 trailblazer and my headlights low beam went out. I checked the fues and the bulbs and they were not blown. please help
  • fj4072fj4072 Posts: 29
    Are both sides out? If so, switch relay # 45 with relay #46. Do you now have lights? If it's just the one side, check the wiring harness and the bulb socket. Some people have problems with the socket overheating and melting.
  • jules712jules712 Posts: 1
    I have an '06 TrailBlazer, & I just want to know how you replace the bulb in passengers side headlight. I was stopped last night & found out it was out, so now I have to figure it out & install it myself. Clear instructions would be helpful, since I really didn't see much of that on here. Thank you! :confuse:
  • jbs_fancijbs_fanci Posts: 3
    edited April 2011
    Raise the hood. The front grill pops right off by carefully pulling at the areas where it is clipped onto the is plastic so be careful. Once you have the grill laid aside you need to stand in front of the passenger headlight. Look directly down at the top area that is under the hood & you will see that there are 2 on the extreme outter top on both will need pliers, etc to pull them straight UP....the one to the far outside is a bit under the fender edge & I used a long screwdriver to tug it up. Make sure you are right in front of the light to catch it so it does not fall. You need to remove the old light & replace with a new one....BUT I had done this TWICE and the exact same light kept going out. The problem is not always the bulb. In my case (and MANY others i have read about) the wiring that attaches to the piece where the bulb goes gets too hot and melts (once you are into the headlight area make sure to look it all over for melted or discolored wiring). My hubby had to fix my wiring & once he did it has never happened again. GOOD LUCK & BE CAREFUL!! Oh...a test you can do BEFORE removing everything to see if it possibly may be the wiring (or this is what we did) is to have your lights ON & use the outside of your fist and thump several times on the passenger side fender area close to the front where the light is. It didn't fix it everytime we did it, but MANY times we'd thump the fender & the light would come back on :)
  • fj4072fj4072 Posts: 29
    Easiest way to do this.....Remove the top of the air cleaner, at this point you have complete access to the bulbs. Remove the 3" round rubber boot, and remove the bulb. There is another way which involves removing the grill, but you chance cracking or breaking the grill and it takes too long.
  • gmcustsvcgmcustsvc Posts: 4,251

    Just checking in to see if the issue has been taken care of. Please keep us posted.

    Thank you,
    Caron, GM Customer Service
  • mfllngmmfllngm Posts: 1
    Both of my headlamps went out, I swapped #45 and #46 like someone had suggested, the lights started working. I went to auto parts store purchased a new relay. Installed the new one, made sure lights worked. They did! That was done in the morning, that night I went to leave and both headlamps out again. Swapped them again they worked, but what would have made the new module go out that I just purchased or what can I do now? i do not want to go to the dealership!!!
  • Hi. I have a 2005 Chevy TB and my lights have been mysteriously shutting themselves off while I am driving down the road. I do not want to take to a dealer so I am hoping that doing what you did - replacing the relay. Have your lights continued working after thhis replacement? It is only my regular beams. The parking lights will continue to work and my brights will turn on. I just don't want to be driving at night and then my lights go out on me!
  • fj4072fj4072 Posts: 29
    edited September 2011
    I've dealt with this myself for 3 years now. Originally I went out and bought a relay. However, I tried taking the old relay out and putting it back in several times (10-15 times) which in turn cleaned the relay and fuse box terminals. My old relay has worked fine for 3 years since this cleaning, however, just recently went out on me completely. When removing the relay, make sure it's not super hot. If it is, replace it. I always keep a spare relay in my glovebox in case I run across someone with this problem. My new relay has been working great and is much cooler than the old one. Sometimes the old relays solder joints on the inside of it will crack, causing arcing which will make it hot......just replace it. I expect that at some point in time that my new relay will stop working in due time (temporarily), but it will be years. Just needs to be cleaned, not sure why, but that relay oxidizes very easily, and is the most common problem with TB's. 3 years ago, I had to special order the part....NO ONE had it in stock. 3 years later, everyone has this in stock, it's that common.

    On a side note, if your lights go out on you, just switch relay #45 and 46, your lights will start working again. But keep an eye on your temperature, the other one controls your fan. Like me, if you do need to switch relays, you're check engine light will eventually go on. Reason- there will be no communication for your fan to turn on and off. Which will throw an OBDII code (don't remember the #), but it's "lost communication with the fan" Just switch them back or replace the bad relay, the check engine light will go off automatically.
  • This forum is so awesome I was about to spend $300 to have someone fix my lights. I have been experiencing the problem of both headlights low beam going out on me. I dont understand why. Please help me to understand what you are saying to do. Do I take 45 relay and put 46 in its spot? Do i need to leave something in 46 also? I am clearly not a mechanic and do not know where this is located but am willing to figure it out. Anything I can do to save some money will help. I appreciate your info.
  • Yes, just switch the two relays to get you out of a jam. So #45, put in the #46 slot, and vis versa. Don't want to leave it too long or you'll get a check engine light for no communication to your fan. The fuse box under the hood, next to the battery is where they are located. The plastic cover has a schematic of the locations of the black colored relays, they are right next to each other. Buy a new relay, $40 from Autozone.

    My explanation of "why" is a thread or two above yours. The 2 problems are basically oxidation of the terminals, and cracked solder joints in the relay itself. Enjoy your $260 you didn't have to spend!
  • I have an 02 Trailblazer. I was lucky enough to get pulled over because my headlight was out. Thought no big deal. I ran up to Autozone the next day and bought a set. Replaced them and but of course, the drivers light is still out. I checked all the head light fuses and I didn't see any that were blown. I made sure the connection was tight and the connector itself seemed fine. I have no clue and I'm living off a student loan so I don't really have money to go to a shop and since I'm in a small town, that cop will probably ticket me next time! Any advice would be GREATLY APPRECIATED. Once again, thank you.
  • When it comes to individual lights not working, count the relay problem out.
    There is a known problem with the connector itself melting on the inside. Have you checked this out, or is that connector getting power? Hook a meter to it and see if you get power. Many people have needed to buy that pigtail and replace with a high heat ceramic connector. The wires going to the connector are too small for the amount of heat that goes to it. Which is why I use standard bulbs, not the extra brights ones you can buy, which draw more heat. On a side note, (just in case you don't know), you cannot touch the bulb itself with bare hands, the oil from your hands will burn a hole in that bulb really quick. Another thing to check, try switching bulbs from the one that works.
  • I have a 2005 ext-ls, I also had the problem with the headlights going out. I switched #45 and #46 relays and they worked fine, I bought a new relay at Advanced Auto for 34.99 and tax. Also my rear stereo speakers and cruise control were not working and the new relay fixed that problem as well (strange but they must be connected somehow). I will mention that my check engine light came on and the codes were for the fan cluch, fan cluch sensor and oxygen sensor, I replaced all and added a k&n cold air intake new plugs and cleaned the throttle body and mass air flow sensor, (the throttle body clean is apparently a necessity with the l6 every year or 20k miles) I mention the fan and cluch because I bought the truck used and suspect the dealer swapped the relays and reset the check engine light this caused the fan cluch and sensor to get defective 2 months after the purchase.
    Next question- after installing the new parts I reset the check engine light. During the first drive it came back on, Advanced Auto says the only code its throwing out is for the mass air sensor is detecting cold air. I susspect its the new intake, is this normal?

    Thanks for all the great info on this site!!!!!!!!!!!!
  • fj4072fj4072 Posts: 29
    FYI, when ever you have a check engine light, the cruise control is disabled which is normal. When the light is reset or goes out, it will work again. Never heard of the rear speaker going out like that. When you switch relay #45 and #46, you will get a check engine light either immediately or shortly after the switch, this is normal. The other relay runs the fan clutch operation, so that's what that is (happened to me also). The oxygen sensor, must of been coinsidence that it was going bad. Yes clean that Throttle body puppy once a year or more often if needed. Really no good way to clean our MAS , buy a new one, cleaning doesn't seem to work for us.

    As for your last question, having a new MAS MAY solve that light, however, I'd call K&N myself. They have an awesome technical department that could answer your question.
  • Hi all-

    I wish I had found this forum sooner; I have a feeling it would have saved me some $. My daughter has a 2006 Trailblazer and the low beams suddenly stopped working. Took it to a mechanic who at first thought it was a switch, then decided it was the body control module. So, $500 later, we have low beams. My question is this---Is the BCM where the relays are? It seems like relays are the popular choice here for fixing the problem...I probably got hosed for my $500, but I couldn't have her driving around with her high beams on. Any advice?
  • fj4072fj4072 Posts: 29
    edited November 2011
    No, the relays are in the fuse box. The BCM (Body Control Module) doesn't have anything to do with the low beam headlights.

    This relay problem can and IS intermittent. So if the relay itself wasn't taken out and or either replaced or cleaned, your low beam lights will eventually go out again. I would ask if this was done. If not, I'd encourage you to replace it yourself. It's about $40 or less, the fuse box is located right next to the battery on the drivers side. Take the top off the fuse box, then take the plastic piece off too. Both just pull up, no tools needed. Look at the bottom of the cover and look at either #43 or #46 relay, it's one of these two. They are both right next to each other, I believe it's the one closest to the firewall. Pull it up and out and replace. Will take ya 15 seconds to do. Good luck!
  • As the previous messaged indicated, the relays are in the fuse box
    under the hood. I got my relpacement at a chevy dealer, just under $40.
    Very easy to replace...
  • Information on the fuse block begins on page 5-109 in the Trailblazer owner's manual. It should be on the driver's side of the vehicle. There's a diagram in there, as well, detailing the different fuses and relays and their locations.

    Hope this helps,
    GM Customer Service
  • My daughter was stopped for having the driver side headlight out on our 2005 trailblazer. When I took it up to have the bulb replaced, they said that the bulb wasn't the problem, it was the contactor. Can this part be purchased at Autozone or someplace similar or does it have to come from a Chevy dealer?? If it has to come from GM, where can I get the part number so that I can order it online??
  • fj4072fj4072 Posts: 29
    You mean connector right? Go to and buy it there, they are cheap and ship same day. Depending on which part you need there, use a high heat connector as this is a very common problem for us Trailblazer owners. has pictures there so you can match up perfectly, don't shy away from Dorman brand as it is a quality brand. Tons of us TB owners use this website to order parts because of they have price AND service....No I don't work for them :), just many great experiences with them myself. They have shipped within an hour many times for me.
  • rules!!!
  • First noticed that the left turn signal was doing double time which normally means a bulb out. Checked all bulbs and all are working. When I jiggled the high beam switch (same as turn signal) it would blink normally. Then next time start double time again. After a while when the high beam is on the left turn signal will blink once then stop. (Really not sure if related or not but the green arrow indicator on the dash stays dimly lit all the time. May be just picking up light from bulb behind meter cluster?)

    Also noticed that ALL front lights on the driver side are more dim than passenger side (high and low beam and turn signal and running light). It is very noticeable when driving. Not sure if the two situations are related.

    Here is what I have tried so far:

    Swapped the real tail light circuit boards. No change.
    Swapped the front head light assemblies. The one from the passenger side that had been bright became dim on the driver side and the driver side assembly became bright on the passenger side. So I am assuming it is not the lights, connections etc. as the problem stayed on the driver side even though the parts were changed.

    Checked voltage on both front sides. Reading just over 14 volts (same both sides).

    I swapped the high beam relay in the fuse box with another relay. No change.

    The turn signal relay uses the same relay for both right and left and em flashers (which flash normal speed by the way) so I don't think it is bad.

    My only thought now is that the turn signal switch is bad but a new one is $100+ so don't want to buy one if not needed. It may be causing the fast blinking, but not sure about the dim lights. Anyone have anything like this happen? I have read about some crazy electrical issues with the TB but nothing like this.
  • Ok more info for post 159 above- after checking today and noticing that the high beam light flashed when the turn signal was on (I could not imagine an electrical system where the high beam would be on the same circuit as the turn signal). Anyway, I was going to take the fuse box apart to see if there was anything melted or shorted out underneath and noticed that all the bolts were already loose (hand loose). I tightened them all up and PRESTO all the problems went away!! So after several hours of messing around I lucked into the fix. I think the dealer left the screws loose a while back they had to do some electrical work. The issues did not start right away so I did not make the connection (no pun intended). p.s. This vehicle is trouble waiting to happen! I would sell it but it's not mine!!
  • My lights have been staying on and draining my battery. I have a 2003 trailblazer. I have replaced my relay for the dimmers. We haven't ruled out #46 relay yet will be doing that tonight. I am almost positive it is not #46. Has anyone had this problem or have any other ideas of what it might be?
  • fj4072fj4072 Posts: 29
    After your vehicle is turned off or what? The TB's I've seen and it's been many, #46 has been stuck in the on position when the battery is being drained. If you're talking about the daytime running lights, there is an off switch. OR you could install a DRL killer.
  • Yes, after I turn the car off my daytime lights stay on and drain my battery. I went to buy #46 and it is $34.00 with no refund. I want to rule out all the possibilities before I buy this part and it be something else. Thinking it could be sensor or somethng in the wiring but not for sure. Where is the off switch? The different light settings switch inside the car does not work when I try to turn them off.
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