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2020 Outback Battery Drain - Dead After a Few Days

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Mike T. · rep 0 · May 24, 1:25 PM · 1 replies · solved · Question

Vehicle: 2020 Subaru Outback Limited

Hey everyone,

I'm having a persistent issue with my 2020 Subaru Outback Limited. If I don't drive it for 2-3 days, the battery is completely dead. I've had the battery tested at AutoZone, and they said it's good, holding a charge fine after they jump it.

This started happening a couple of months ago. No new accessories installed recently, everything is stock. I've checked the interior lights, and they all seem to turn off.

Could this be a parasitic draw? What are some common culprits on these newer Outbacks? Any tips on what to check before I take it to the dealer? Thanks in advance!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 1:25 PM

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ClearTheCode admin answer:

A parasitic draw is a very common cause of battery drain, especially on modern vehicles with numerous electronic modules. Here's a breakdown and what you can do:

  1. Confirm Parasitic Draw:

    • Charge your battery fully.
    • Disconnect the negative battery terminal.
    • Connect an ammeter in series between the negative battery post and the disconnected negative cable.
    • Wait 15-30 minutes for all modules to 'sleep'. A normal draw should be around 20-50 milliamps (0.02-0.05 amps). Anything significantly higher indicates a problem.

  2. Common Causes on Subaru Models (2016-2026):

    • Starlink Telematics Module: This is a frequent culprit. Issues with the module can prevent it from entering sleep mode, causing a constant draw.
    • Aftermarket Accessories: Even if not recent, poorly wired dash cams, remote starters, or audio equipment can cause a draw.
    • Faulty Relays: A relay stuck in the 'on' position can keep a circuit active.
    • Body Control Module (BCM) or Infotainment System: Malfunctions in these complex modules can sometimes lead to excessive power consumption.
    • Alternator Diode Failure: Less common for a full drain when off, but a failing diode can allow current to flow back through the alternator.

  3. When to See a Shop:

    • If your ammeter test shows a high draw and you're uncomfortable pulling fuses to isolate the circuit, it's best to see a qualified technician.
    • A Subaru dealership or an independent shop with Subaru diagnostic tools can pinpoint the exact module or circuit causing the draw. They can check for specific Diagnostic Trouble Codes (DTCs) related to module communication errors or low voltage, although a parasitic draw itself might not always trigger a specific OBD-II code directly until the voltage drops too low (e.g., P0562 - System Voltage Low).
    • They can also perform a 'draw test' more efficiently and safely, often with specialized equipment that can monitor individual circuit draws without repeatedly disconnecting the battery. Addressing this promptly will prevent premature battery wear and potential damage to other electrical components.
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