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

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Diana O. · rep 0 · May 22, 4:49 AM · 1 replies · solved · Question

Vehicle: 2018 Mazda CX-5 Grand Touring

Hey everyone,

I've got a 2018 Mazda CX-5 Grand Touring, and lately, I've been having some weird electrical issues. The battery seems to be draining much faster than it should. If I leave it parked for a couple of days, it struggles to start, and sometimes needs a jump.

On top of that, the i-Stop (start-stop) system hasn't been engaging at all. I know it can be sensitive to battery charge, so I'm wondering if these two problems are related. I had the battery tested at a local auto parts store, and they said it was okay, but I'm not entirely convinced.

Has anyone experienced this with their CX-5? Could it be a parasitic draw, or maybe something with the charging system? Any advice on what to check first would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:49 AM

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ClearTheCode admin answer:

It sounds like you're dealing with a classic parasitic draw or a failing charging system, both of which would affect your i-Stop functionality. The i-Stop system requires a healthy battery and charging system to operate correctly.

  1. Check for Parasitic Draw:

    • Diagnosis: A parasitic draw occurs when components continue to draw power even when the car is off. You can test this with a multimeter. Disconnect the negative battery terminal, connect the multimeter in series between the negative terminal and the battery post (set to amps). Wait for about 20-30 minutes for all modules to 'sleep.' A normal draw is usually under 50mA. If it's higher, start pulling fuses one by one until the draw drops, indicating the circuit with the issue.
    • Common Culprits: Aftermarket accessories, faulty modules (e.g., infotainment, door lock actuators), or a stuck relay.

  2. Inspect the Charging System:

    • Alternator Output: Even if the battery tests 'okay,' a weak alternator might not be fully recharging it. With the engine running, check the voltage across the battery terminals. It should be between 13.5V and 14.5V. If it's consistently lower, the alternator might be failing.
    • Battery Condition: While the store said it was okay, a battery can have good voltage but low cold-cranking amps (CCA), especially if it's nearing the end of its life (typically 3-5 years). A professional load test is more accurate than a simple voltage check.

  3. OBD-II Codes:

    • A low system voltage can sometimes trigger codes like P0562 (System Voltage Low). While your check engine light might not be on, a deeper scan with a more advanced tool might reveal pending or historical codes related to voltage or specific module malfunctions.

When to See a Shop: If you're uncomfortable performing electrical tests or if you identify a high parasitic draw but can't pinpoint the exact component, it's best to take your CX-5 to a qualified mechanic. They have specialized tools and diagnostic equipment to quickly identify and resolve complex electrical issues, ensuring your vehicle's electrical system is functioning optimally and safely.

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