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2018 RX 350 Battery Draining Fast, "Check Charging System" Light

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Mike T. · rep 0 · May 25, 3:28 AM · 1 replies · solved · Question

Vehicle: 2018 Lexus RX 350 F Sport

My 2018 Lexus RX 350 F Sport has been giving me trouble lately. The battery seems to drain really fast, especially if I don't drive it for a day or two. A few times, I've had to jump-start it.

Yesterday, the "Check Charging System" light came on while I was driving. I'm worried I might get stranded. The car has about 65k miles on it.

Could this be just a bad battery, or something more serious like the alternator? What should I check first?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:28 AM

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ClearTheCode admin answer:

  1. Diagnose the Battery: Start by having your battery tested. Many auto parts stores offer this service for free. Even if the battery is relatively new, a faulty cell can cause rapid discharge.
  2. Check Alternator Output: If the battery tests good, the next step is to check the alternator's output. With the engine running, a healthy alternator should be putting out between 13.5 and 14.5 volts at the battery terminals. A reading below this range indicates a failing alternator.
  3. Inspect Connections: Ensure all battery terminals are clean, tight, and free of corrosion. Also, check the main ground strap from the battery to the chassis and engine for secure connections. Loose or corroded connections can impede proper charging.
  4. Parasitic Draw Test: If both the battery and alternator check out, you might have a parasitic draw. This means something is staying on and draining the battery even when the car is off. This can be tricky to diagnose and often requires a multimeter to test current draw across fuses. Common culprits include aftermarket accessories, faulty modules, or interior lights not turning off.
  5. OBD Codes: A "Check Charging System" light often accompanies codes like P0562 (System Voltage Low) or P0563 (System Voltage High). Scanning for codes can provide more specific direction.

When to See a Shop: If you've tested the battery and alternator and the problem persists, or if you're uncomfortable performing electrical tests, it's best to take your Lexus to a qualified mechanic. A parasitic draw can be complex to trace, and a professional can quickly identify and rectify the issue, preventing further battery damage or potential breakdowns. Ignoring a charging system warning can lead to being stranded or damage to other electrical components.

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