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2020 CX-5 i-Stop Not Engaging & Battery Draining Fast

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Brian F. · rep 0 · May 22, 4:50 AM · 1 replies · solved · Question

Vehicle: 2020 Mazda CX-5 Grand Touring

My 2020 Mazda CX-5 Grand Touring has been acting up lately. The i-Stop system, which usually works fine, hasn't been engaging at all for the past few weeks. It's usually a feature I appreciate for fuel economy.

On top of that, I've noticed the battery seems to drain much faster than it used to. If I leave it for a couple of days, it struggles to start, sometimes needing a jump. I had the battery tested at an auto parts store, and they said it was "weak" but not dead.

Could this be related to a sensor, a module, or just a failing battery? I'm trying to figure out if it's something simple I can check myself before taking it to the dealer.

✓ Accepted solution

ClearTheCode Admin

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

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ClearTheCode admin answer:

It sounds like you're dealing with a common set of symptoms that often point to battery or charging system issues, which can directly impact the i-Stop system's functionality. The i-Stop system requires the battery to be in excellent condition and fully charged to operate.

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

  1. Battery Health: Even if an auto parts store says the battery is "weak," it might not be sufficient for the i-Stop system's demands. A battery that's 3-5 years old is often at the end of its life, especially in climates with extreme temperatures. A proper load test at a shop can give a more definitive answer.
  2. Parasitic Draw: A "weak" battery that drains quickly could indicate a parasitic draw – something in the vehicle is consuming power even when the car is off. This could be a faulty module, an aftermarket accessory, or even a dome light left on. Diagnosing this requires specialized tools to measure current draw.
  3. Charging System: The alternator might not be charging the battery effectively. A failing alternator can lead to a constantly undercharged battery. You might see a P0562 (System Voltage Low) or P0563 (System Voltage High) code if there's a charging issue.
  4. i-Stop System Requirements: The i-Stop system has several conditions that must be met before it engages, including engine temperature, cabin temperature, steering angle, brake pedal pressure, and crucially, battery state of charge and health. If the battery isn't optimal, i-Stop will disable itself.

When to see a shop:

  • If replacing the battery doesn't resolve the issue, or if the new battery also drains quickly.
  • If you suspect a parasitic draw, as this can be complex to diagnose without proper equipment.
  • If you're getting any check engine lights or specific battery/charging system warnings.
  • If the alternator output needs to be tested under various loads.

It's best to have a qualified Mazda technician perform a comprehensive electrical system diagnostic to pinpoint the exact cause of the battery drain and i-Stop malfunction.

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