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2018 Sorento SX Battery Draining Overnight - Electrical Gremlin?

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Mike T. · rep 0 · May 24, 1:24 PM · 1 replies · solved · Question

Vehicle: 2018 Kia Sorento SX

Hey everyone,

I'm having a really frustrating issue with my 2018 Kia Sorento SX. For the past few weeks, the battery keeps dying, sometimes overnight, sometimes after just a couple of days of sitting. It's completely dead, no lights, no nothing. I've had the battery tested twice, and both times it came back as perfectly healthy. The alternator was also checked and is charging fine.

It feels like something is constantly drawing power, even when the car is off. I haven't added any new aftermarket accessories recently, so it's not an obvious culprit. Has anyone else experienced a parasitic battery drain on their Sorento or other Kia models from this era? What did you find was the problem, and how was it fixed?

I'm dreading taking it to the dealership without any idea, as electrical issues can be so hard to track down. Any advice or shared experiences would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 1:24 PM

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ClearTheCode admin answer:

It sounds like you're dealing with a classic parasitic battery drain, which can indeed be a headache to diagnose. Since your battery and alternator have tested good, the focus should definitely shift to identifying the component that's drawing power when the vehicle is off.

  1. Understanding Parasitic Drain: A parasitic drain occurs when an electrical component continues to draw a small amount of current from the battery even after the vehicle has been shut off. While a small amount is normal (for things like the clock, radio memory, etc.), an excessive drain will kill your battery.

  2. Common Causes in Kia Vehicles:

    • Faulty Control Modules: The Body Control Module (BCM), infotainment system, or even individual door modules can sometimes fail to 'go to sleep' properly, remaining active and drawing power.
    • Stuck Relays: A relay that's stuck in the 'on' position can keep a circuit energized.
    • Aftermarket Accessories: Even if not recent, an improperly installed or malfunctioning aftermarket alarm, remote start, or audio system can be a culprit.
    • Ignition Switch Issues: Less common, but a faulty ignition switch can sometimes fail to cut power to all circuits.
    • Interior/Trunk Lights: A light that stays on due to a faulty switch (e.g., glove box, trunk) can drain the battery.

  3. Initial DIY Troubleshooting (Requires a Multimeter):

    • Measure Current Draw: With the vehicle off and all doors closed (or latches simulated), disconnect the negative battery terminal. Connect a multimeter in series between the negative battery post and the disconnected negative cable (set to measure amps). Wait at least 15-30 minutes for all modules to power down. A healthy draw is typically under 50 milliamps (0.05 amps). If it's significantly higher, you have a drain.
    • Fuse Pull Test: While monitoring the current draw, systematically pull one fuse at a time from both the under-hood and interior fuse boxes. When the current draw drops significantly, you've identified the circuit where the drain is occurring. This narrows down the search considerably.

  4. When to See a Shop:

    • If you're uncomfortable performing the multimeter test or can't pinpoint the circuit, it's best to take your Sorento to a qualified automotive electrical specialist or your Kia dealership. They have advanced diagnostic tools (like scan tools that can monitor module sleep states) and experience with these types of issues.
    • While parasitic drains often don't throw specific OBD-II codes directly related to the drain itself, a malfunctioning module causing the drain might log a 'U' code (e.g., U0100 for lost communication with ECM/PCM A) or other communication errors that a professional can interpret.
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