Need advice -- electrical system issue? low beams quit working

[Caitlin Ellingson]

Hi guys, just looking for some advice. 

 

The issue: I recently had my battery replaced and shortly after this was done my low beams (both sides) quit working. The next day my stereo started turning off and on again, and there's a message on the dash saying "service theft deterrent system" with the lock symbol. I can still drive it though (not at night) and it doesn't lock me out. I checked the fuses and relay for the low beams and they seem fine. I haven't checked the bulbs yet but it seems too coincidental that both would go out at the same time, though I could be wrong. 

 

In case this is relevant info: I had the battery replaced a month ago via AAA, but it turned out to be from a bad batch. It died after a few weeks while I was conveniently at a local shop getting a wheel alignment, so the mechanic there jumped it twice (once to get it onto the rack and another to get it back in the parking lot). They showed me how the interior lights were flickering before shutting it off (I didn't see the headlights at that point).  AAA replaced the battery in the lot after that since it was under warranty. 

 

Any suggestions would be appreciated. I'll take it to a mechanic next week but I wanted to do some research first to see if there's an easy fix I may have missed. Truck is a 2011 GMC Sierra 1500 SLE.  

 

Thanks!

Caitlin

[richard wysong]

Welcome to the forum! Is there power at the fuses and relay? I would check in the vicinity of the battery and see if there is a ground or power wire that got broken or has corroded connections. Do the high beams still work? If all that is ok  next step is to determine if there is power and ground at the bulbs before chasing further. Possibly a bad light switch but that doesn't explain the security light

[Caitlin Ellingson]

Thanks  

 

There appears to be power at the fuses/relay, but I wasn't 100% sure about the relay so I ordered a replacement -- and I also ordered a circuit tester (both should arrive soon). The high beams appear to work properly.  I'll definitely check around the battery -- I did a quick look last night but the lighting in my garage wasn't too great. Appreciate the help!

[richard wysong]

relay failure is extremely rare, there is usually another of the same relay in the box so  switching them around is an easy way to check them .test light is a very useful tool for doing quick checks of fuses, grounds etc. If the hi-beams work it's probably not the switch. When you get your tester check all the fuses, both fuse boxes

Edited December 1, 2022 by richard wysong

[64BAwagon]

Just a WAG but I would look towards the turn signal/high beam switch as the issue. You could pull the relay for the low beams and see if there is a signal to it, compare it to the high beam relay input.

[Douglas Nathan]

I would discount the battery from the issue, batteries do not target systems for sabotage; batteries either have, almost have, or don't have enough voltage to do the job. Batteries (like anything else mass produced) can have batch issues so you can't really blame AAA or the battery. I think you got a switching issue; if it's a ground issue clean the grounding point and the terminals on the wires that go there, use dielectric grease to inhibit further corrosion growth.