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2018 S90 T6 Battery Drain & Start-Stop Not Working

0

Mike T. · rep 0 · May 22, 5:15 AM · 1 replies · solved · Question

Vehicle: 2018 Volvo S90 T6 Inscription

Hi all,

I've been having some trouble with my 2018 Volvo S90 T6 Inscription. Over the past few weeks, I've noticed that if I leave it parked for more than a couple of days, the battery is completely dead. I've had to jump-start it multiple times. On top of that, the Start-Stop function hasn't been working at all, which I know can be related to battery health.

I'm worried there's a parasitic draw somewhere, or maybe the battery itself is just shot. Has anyone experienced this with their S90? What should I be looking for? I'm trying to avoid an expensive diagnostic if it's something simple.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:15 AM

0

ClearTheCode admin answer:

Battery drain and non-functional Start-Stop are classic symptoms of a weak battery or a parasitic draw in your 2018 Volvo S90. Here’s how to approach it:

  1. Check Battery Health:

    • The primary 12V battery might simply be at the end of its life, especially if it's the original. Have it tested at an auto parts store or a mechanic. A failing battery often triggers the Start-Stop system to disable itself to conserve power.
    • Volvo vehicles also have an auxiliary battery (often for the Start-Stop system itself). This battery can also fail and impact the main battery's performance or the Start-Stop function.

  2. Look for OBD Codes:

    • A weak battery can trigger codes like P0562 (System Voltage Low) or P0620 (Generator Control Circuit Malfunction) if the alternator is struggling to keep up due to a failing battery or excessive draw.

  3. Test for Parasitic Draw:

    • This is a more involved test, but it involves using a multimeter to measure current draw from the battery when the car is off and all systems are asleep. A draw above 50mA-70mA is usually indicative of a problem. You would then pull fuses one by one to isolate the circuit causing the draw.

Common Causes:

  • Aging Battery: The most common culprit. Batteries typically last 3-5 years.
  • Failing Auxiliary Battery: Specifically impacts Start-Stop and can put a strain on the main battery.
  • Faulty Alternator: Not charging the battery properly. You might see a battery light on the dash.
  • Parasitic Draw: A module (e.g., infotainment, alarm, comfort access) not shutting down correctly, continuously drawing power.

When to See a Shop:

  • If battery testing confirms the battery is good, but the drain persists.
  • If you're uncomfortable performing a parasitic draw test yourself.
  • If the alternator is suspected to be faulty (check voltage output while the engine is running).
  • If diagnostic codes point to specific electrical modules or charging system failures.
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