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2022 Terrain Headlights Flickering and Dimming Intermittently

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Eric V. · rep 0 · May 22, 3:42 AM · 1 replies · solved · Question

Vehicle: 2022 GMC Terrain SLE

Hi all,

I've got a weird electrical problem with my 2022 GMC Terrain SLE. The headlights, both high and low beams, have started flickering intermittently. It's not constant, but it happens enough to be noticeable and a bit concerning, especially at night. Sometimes they also seem to dim slightly for a second or two before returning to normal brightness.

It doesn't seem to be related to bumps or turning the steering wheel, just random. I've checked the bulbs, and they look fine, and it's happening to both sides, which makes me think it's not just a bad bulb.

Could this be a relay, a wiring harness issue, or something with the BCM? Any advice on where to start looking would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:42 AM

0

ClearTheCode admin answer:

Intermittent flickering and dimming of both headlights on a newer vehicle like your 2022 GMC Terrain SLE can be a tricky issue to diagnose, as it points to a common power supply or control problem rather than individual bulb failure. Here are the most likely culprits and diagnostic steps:

  1. Charging System Check: A fluctuating voltage from the alternator can cause lights to flicker. Have your battery and alternator tested. Even minor voltage drops can affect sensitive LED or HID systems.
  2. Ground Connections: Poor or corroded ground connections are a very common cause of electrical gremlins. Check the main battery ground, engine ground, and any ground points specifically for the front lighting system. A loose ground can cause resistance and voltage drops.
  3. Headlight Relay/Fuse Box: While less common for both lights, a faulty main headlight relay or issues within the fuse box (corroded terminals, loose fuses) could cause intermittent power delivery. You might try swapping the headlight relay with a known good, identical relay from another non-critical circuit (e.g., horn relay) to test.
  4. Body Control Module (BCM): The BCM controls many electrical functions, including lighting. A faulty BCM or a software glitch within it could send erratic signals to the headlights. This would typically require dealership-level diagnostics.
  5. Wiring Harness Inspection: Look for any signs of chafed, pinched, or corroded wiring in the headlight circuits, especially where they pass through the engine bay or near moving parts.

When to See a Shop:

  • If basic checks of the battery, alternator, and visible wiring don't reveal the problem, it's best to consult a professional. Modern lighting systems are complex and often integrated with the BCM.
  • A dealership or a specialized auto electrical shop will have the diagnostic tools to scan the BCM for fault codes (even if no dashboard light is on) and perform advanced voltage drop tests to pinpoint the exact source of the flickering.
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