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Battery Warning Light On in 2020 Ascent - Alternator or Battery?

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Mike T. · rep 0 · May 25, 2:16 AM · 1 replies · solved · Question

Vehicle: 2020 Subaru Ascent Touring

My 2020 Subaru Ascent Touring just had its battery warning light come on while driving. The car seems to be running fine, no noticeable power loss or dimming lights yet, but I'm worried it's going to die on me.

I had the battery tested a few months ago, and it was good. Could this be the alternator going out, or maybe just a loose connection somewhere? What should I check first before taking it to a mechanic?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:16 AM

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ClearTheCode admin answer:

The battery warning light illuminating on your 2020 Subaru Ascent Touring is a critical indicator that there's a problem with your vehicle's charging system. While the car might seem fine now, it's likely running solely on battery power, which will eventually deplete.

  1. Understand the Light: The battery light doesn't necessarily mean your battery is bad; it means the charging system (primarily the alternator) is not adequately charging the battery. The battery's job is to start the car, and the alternator's job is to keep it running and recharge the battery.
  2. Check Battery Terminals: Safely pull over and visually inspect your battery terminals. Ensure they are clean, tight, and free of corrosion. Loose or corroded terminals can interrupt the charging circuit. A quick clean and tighten might resolve the issue.
  3. Inspect Serpentine Belt: The alternator is driven by the serpentine belt. With the engine off and cool, check the serpentine belt for any signs of damage, fraying, or if it has come off its pulleys. If the belt is broken or loose, the alternator won't spin and won't charge.
  4. Test Battery Voltage (Engine Off): If you have a multimeter, set it to DC volts. With the engine off, check the voltage across the battery terminals. A healthy battery should read around 12.6-12.8 volts.
  5. Test Charging Voltage (Engine On): With the engine running, place the multimeter probes on the battery terminals. The voltage should ideally be between 13.5 and 14.5 volts. If it's still around 12 volts (or lower), your alternator is likely not charging.
  6. Look for OBD Codes: A failing charging system can trigger specific diagnostic trouble codes (DTCs) related to voltage regulation. Common codes include:
    • P0562: System Voltage Low
    • P0563: System Voltage High
    • P0620: Generator Control Circuit Malfunction

When to See a Shop: If your battery terminals are clean and tight, the serpentine belt is intact, and especially if your multimeter shows low voltage with the engine running, it's highly probable your alternator is failing. You should drive your 2020 Ascent to a repair shop or Subaru dealership immediately. Driving for too long with a non-charging alternator will drain the battery completely, leaving you stranded. A professional can confirm the alternator's health and replace it if necessary.

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