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2018 Sierra 1500 Battery Draining Overnight - Help!

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Mike T. · rep 0 · May 25, 2:39 AM · 1 replies · solved · Question

Vehicle: 2018 GMC Sierra 1500 SLT

Hey everyone, I'm pulling my hair out with my 2018 GMC Sierra 1500 SLT. For the past few weeks, the battery keeps dying overnight. I've replaced the battery twice, and the alternator tests fine. It seems like something is drawing power even when the truck is off.

I've checked for obvious things like lights left on, but everything seems to be off. Sometimes, I notice the infotainment screen takes a while to completely shut down, or a faint clicking from under the dash.

Has anyone experienced this with their Sierra? What should I be looking for? It's becoming a real pain to jump-start it every morning.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:39 AM

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ClearTheCode admin answer: A parasitic battery drain on your 2018 GMC Sierra 1500 SLT indicates a component is drawing power when the vehicle is off. This is a common, albeit frustrating, electrical issue.

Here’s how to approach it:

  1. Perform a Parasitic Draw Test:

    • Disconnect the negative battery terminal.
    • Connect a multimeter in series between the negative battery post and the negative battery cable (set to Amps).
    • Allow the vehicle to "go to sleep" (can take 15-30 minutes for all modules to shut down). A normal draw should be under 50 milliamps (0.05 amps).
    • If the draw is too high, start pulling fuses one by one from both the under-hood and interior fuse boxes until the draw drops significantly. This will help isolate the problematic circuit.

  2. Common Causes:

    • Infotainment System/Radio: As you mentioned, a module not shutting down properly can cause a drain.
    • Body Control Module (BCM): A faulty BCM can keep various systems active.
    • Aftermarket Accessories: Anything added after purchase (remote start, alarm, sound system) can be a culprit if wired incorrectly.
    • Glove Box/Trunk Lights: Stuck switches can keep these lights on, even if not visible.
    • HVAC Blower Motor: Sometimes these can run intermittently or not shut off fully.

  3. When to See a Shop: If you're uncomfortable performing the parasitic draw test yourself, or if you've identified a circuit but can't pinpoint the exact component (e.g., pulling the 'Radio' fuse drops the draw, but you don't want to replace the whole unit), it's time to visit a qualified automotive electrical specialist. They have advanced diagnostic tools to pinpoint module failures and trace complex wiring issues, potentially saving you time and further frustration.

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