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2019 NX 300 - 'Check Charging System' Light & Dim Headlights

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

Vehicle: 2019 Lexus NX 300 Base

Hi everyone,

I'm having some electrical problems with my 2019 Lexus NX 300. The 'Check Charging System' warning light came on a few days ago, and I've noticed my headlights are a bit dimmer than usual, especially at idle. The car also seems to crank a little slower when I start it, though it does start.

I checked the battery terminals, and they look clean and tight. I haven't done any recent work on the car. I'm worried this might be an alternator issue, but I wanted to get some opinions before taking it in. Is there anything simple I can check myself?

Thanks for any help!

✓ Accepted solution

ClearTheCode Admin

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

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ClearTheCode admin answer:

The symptoms you're describing in your 2019 Lexus NX 300 – 'Check Charging System' light, dim headlights, and slow cranking – are classic signs of a failing charging system, most commonly the alternator or related components.

1. Battery Health Check:

  • Voltage Test (Engine Off): A healthy battery should read around 12.6-12.8 volts. If it's significantly lower (e.g., below 12.4V), the battery might be weak or not holding a charge.
  • Load Test: Most auto parts stores offer free battery and charging system tests. This is the easiest way to confirm if your battery is still good or if it's struggling to hold a charge.

2. Alternator Output Test (Engine Running):

  • With the engine running, a healthy charging system should produce around 13.5-14.7 volts at the battery terminals. If the voltage is lower, especially around 12V or less, your alternator is likely not charging the battery effectively.
  • Check Serpentine Belt: Ensure the serpentine belt, which drives the alternator, is not loose, cracked, or slipping. A loose belt can prevent the alternator from spinning at the correct speed to generate sufficient power.

3. Wiring and Connections:

  • Battery Terminals: Double-check that your battery terminals are not only clean and tight but also free of any corrosion underneath the clamps. Even slight corrosion can impede current flow.
  • Alternator Connections: Inspect the main power wire and the smaller exciter wire connected to the alternator for any looseness or damage.

Common OBD Codes: If you have access to an OBD-II scanner, you might find codes like:

  • P0562: System Voltage Low
  • P0563: System Voltage High (less likely with your symptoms)
  • P0622: Generator F-Terminal Circuit Malfunction

When to See a Shop: If the battery tests good but the alternator output is low, or if you're unable to perform these tests yourself, it's crucial to take your NX 300 to a qualified mechanic or a Lexus dealership as soon as possible. A failing charging system can leave you stranded. They can:

  • Perform comprehensive battery and alternator tests.
  • Diagnose any related wiring issues.
  • Replace the alternator if it's found to be faulty. Driving with a bad alternator will eventually drain your battery completely, leading to a breakdown.
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