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I have an 02 TrailBlazer LT. Shortly after I bought it I noticed the passenger low beam was burnt out. It also had the wires/plug burnt (some sites i've visited state that later years were not made of the same materials & they believed this to be the issue...but I am unsure). My husband fixed the problem on mine. Not too many months later we were driving down the hiway at night and lost all low beams. Not too sure why I did it, but I instantly flipped over to high beams and they worked fine. Pulled over, turned off the suv & restarted it & low beams were back. This went on for a few months. After searching HERE, on Edmunds, we followed the advice of another poster. Here is a copy of the post we read & followed: Low beams are driven by a module in the underhood fuse block. #46 is the Headlight Driver Module ("HDM") which is a solid-state relay. This is becoming a common failure. You can test it by temporarily swapping it with #45 the "Cooling Fan" driver module for the fan clutch as they are the same type device. If that's it, you will likely have to buy the replacement from a GM dealer. Prices can vary from about $25 to over $40 for that module depending where you buy it. Good Luck!b> **note that hubby & I left modules #45 & #46 this way & never bought a replacement for either & that was about a year back. I've had no trouble with either device ) Hope this helps!!
After going through all the messages on this subject I may have found the answer in switching the relays #45 and #46. My symptoms are somewhat different(I think). When I park the TB after dark and then start it sometime later, the headlights do not work, neither hi or lo will come on. Last night after driving 2 miles and arriving home(miracle) the headlights came back on as I entered my driveway.
It(the problem) may be related to the fact that I had parked under some lights before turning the engine off. This is a stretch but had happened before under those circimstances. Very frustrating and scary.
Thanks again for the recommendation.
Subject:Diagnostic Information on Headlamps Flicker or Momentarily Dim While Driving #05-08-42-001 - (03/07/2005)
Models:2004-2005 Buick Rainier
2002-2005 Chevrolet TrailBlazer
2002-2005 GMC Envoy
2003-2004 Oldsmobile Bravada
with 4.2L Engine (VIN S -- RPO LL8)
A concern regarding headlamps flicker or become dim while driving may be easily mis-diagnosed. It is very important to capture as much information from the customer as possible. Below is a guideline to assist with diagnostics.
Verify the customers specific concern.
• What time of day does this occur (is it light or dark outside) ?
• What driving conditions (vehicle speed, engine speed, throttle position, etc...)?
• What was the outside ambient temperature when the condition occurred?
• What accessories was the driver using when this condition occurred (A/C, heated seats, rear defogger, etc...)?
• If the concern is at dusk, could it be the automatic headlamps changing from DRL to Headlamp mode and possibly back to DRL again?
• Are there any other relevant operating conditions?
Diagnostic Information
• Service Bulletin - 02-06-03-008A - Info - Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, No Start, Slow Cranking, Dim Lights at Idle, Low Generator Output (SI Document ID #1540541)
• Service Bulletin - 02-06-03-006B - No Start, No Crank, Battery, Batteries, Generator, Gages, SES, SIR, Brake, Security, Theft, ABS, Hot, DIC Messages, Lamp, Light, Battery and Generator Diagnostic Testing and Cadillac Roadside Service (SI Document ID #1563904)
• Service Information - Exterior Lighting Systems Description and Operation (SI Document ID #826321)
• Service Information - Battery Inspection/Test (Non-HP2) (SI Document ID #653410)
• Service Information - Charging System Test (SI Document ID #1468059)
• Service Information - Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems (SI Document ID #816776)
Important:
• Keep in mind high current draw items may cause a noticeable dimming of lights and a fluctuation in the voltmeter may be noted and is a normal operating characteristic of the vehicle.
• For 2004-2005 TrailBlazer, Envoy, Rainier and Bravada with the LL8 4.2L engine only, the Secondary Air Injection (AIR) pump activation is thought to be the main contributor to this high current draw condition and is a normal operating characteristic of the vehicle. Refer to Secondary Air Injection System Description (SI Document ID #1298539).
For customers whose driving habits tend to run the AIR pump diagnostic test that leads to concerns with the headlight flickering, if the vehicle is allowed to idle for 20 seconds prior to driving, this should allow the passive test to pass and prevent from running the active test that may dim the lights. The passive test should/will usually pass 99 percent of the time, and by allowing the 20 second idle period, it should almost eliminate the active test. Be sure to check for codes and correct related concerns if this condition repeats.
Additional high current draw items are rear window defogger, HVAC blower motor, rear air suspension pump along with other components.
For easier diagnostics, it may be possible to control or monitor these components with a scan tool.
It is important to inspect all related connections, grounds and battery terminals for integrity . A loose or corroded connection may exaggerate the concern, and may cause other symptoms. Refer to Testing for Intermittent Conditions and Poor Connections (SI Document ID #1470165).
Corrections/repairs should only be made for specific concerns identified and not related to characteristic of high current draw components.
I have experienced problems with cluster panels, low beams, actuators, heating/cooling system, etc. Every problem I have had I came on this forum and it shows people entering tons of problem with the same or related issues. I have even seen reviews from people that has '07 or higher chevy models and they are having these problems and it is ridiculous. I will NEVER buy another chevy/GMC vehicle again. These forums have really helped me to get to the bottom of some of my problems so I could go to a dealership like I know what was going on. But this is ridiculous and chevy does not do a recall on any of this.
I replaced both low beam sockets a long time ago on our 02 with ceramic ones due to the heat causing the plastic ones so soften and deform.
Just checking in to see if the issue has been taken care of. Please keep us posted.
Thank you,
Caron, GM Customer Service
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.
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!
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.
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!!!!!!!!!!!!
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.
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?
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!
under the hood. I got my relpacement at a chevy dealer, just under $40.
Very easy to replace...
Hope this helps,
Sarah
GM Customer Service
rockauto.com 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.
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.
Thanks