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2018 CX-5 Battery Draining Fast, i-Stop Not Working

0

Mark S. · rep 0 · May 22, 4:50 AM · 1 replies · solved · Question

Vehicle: 2018 Mazda CX-5 Grand Touring

My 2018 Mazda CX-5 Grand Touring has been having battery issues lately. The i-Stop system stopped working a few weeks ago, and now the battery seems to drain really fast, especially if the car sits for a day or two. I had it tested at AutoZone, and they said the battery is okay, but it keeps losing charge.

I've checked for obvious things like lights left on, but nothing. It's really frustrating to come out to a dead car. I'm worried about getting stranded.

Has anyone else experienced this with their CX-5? Any ideas on what could be causing this parasitic draw or if it's related to the i-Stop system?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:50 AM

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ClearTheCode admin answer:

Your 2018 Mazda CX-5's symptoms, especially the i-Stop system not working and rapid battery drain, strongly suggest an electrical issue. The i-Stop system is highly sensitive to battery health and charge levels, often being the first feature to disable itself when the battery is weak or there's an underlying electrical problem.

Here's what could be happening and what to do:

  1. Check for Parasitic Draw: Even if your battery tests 'good,' a component could be staying on when the car is off, slowly draining it. This is a common cause of mysterious battery drains. A technician can perform a parasitic draw test using an ammeter to isolate the circuit responsible.
  2. Inspect the Alternator: While less likely if the battery tests okay, a failing alternator might not be charging the battery sufficiently while driving. This can lead to a gradual discharge. Have its output checked under load.
  3. Battery Management System (BMS) Reset/Issue: Mazda's i-Stop system relies on a sophisticated BMS. Sometimes, a simple battery replacement or disconnection requires a BMS reset to properly calibrate the system. If the BMS itself is faulty, it could lead to incorrect charging or discharging.
  4. Diagnostic Trouble Codes (DTCs): A scan tool might reveal codes like P0562 (System Voltage Low), which would indicate a general low voltage condition, or other codes related to the i-Stop system or charging. These codes can help pinpoint the exact cause.

When to See a Shop:

  • If you cannot identify an obvious cause (like a light left on).
  • If the issue persists after ensuring the battery terminals are clean and tight.
  • If you're getting stranded or the car struggles to start frequently.

An automotive electrical specialist or a Mazda dealership will have the specific diagnostic tools to accurately identify a parasitic draw, test the alternator, and diagnose any issues with the i-Stop system or Battery Management System.

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