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2019 S90 T6 Electrical Gremlins & Battery Drain

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Chris P. · rep 0 · May 25, 3:52 AM · 1 replies · solved · Question

Vehicle: 2019 Volvo S90 T6 Inscription

Hey everyone,

I'm having some really strange electrical issues with my 2019 Volvo S90 T6, which has around 55,000 miles. Over the past few weeks, I've noticed a few things: the infotainment system occasionally freezes, some dashboard warning lights (like ABS or stability control) flicker on and off intermittently, and the car seems to be draining its 12V battery overnight if I don't drive it daily.

I've had to jump-start it a couple of times already. I had the battery tested, and it came back as good, so I'm thinking it's not the battery itself, but something is drawing power. I've also checked for any obvious lights left on or accessories plugged in, but found nothing.

Could this be a faulty alternator, a bad ground, or a more complex module issue? It's really frustrating. Any suggestions on where to start looking?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:52 AM

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ClearTheCode admin answer:

Intermittent electrical issues, flickering warning lights, and a recurring battery drain on your 2019 Volvo S90 T6 are classic signs of a parasitic draw or a failing charging system component. Given the complexity of modern Volvo electronics, a systematic approach is essential:

  1. Verify Alternator Function: Even if the battery tests good, the alternator might not be charging it properly while the engine is running. Use a multimeter to check the voltage across the battery terminals with the engine running. It should be consistently between 13.5 and 14.5 volts. If it's lower, the alternator might be failing.
  2. Test for Parasitic Draw: This is the most likely cause of overnight battery drain.
    • Connect a multimeter in series between the negative battery post and the negative battery cable (after ensuring the car is fully 'asleep' – typically 20-30 minutes after locking).
    • A normal draw is usually under 50 milliamps (0.05 amps). If it's significantly higher, you'll need to pull fuses one by one until the draw drops, indicating the circuit with the fault.
  3. Inspect Ground Connections: Loose, corroded, or damaged ground connections can cause a multitude of electrical gremlins, including intermittent warnings and poor module communication. Check the main battery ground, engine grounds, and body grounds. Clean any corrosion and ensure connections are tight.
  4. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to check for any stored codes, especially U-codes (communication errors) or B-codes (body electrical issues). These can point to specific modules that are malfunctioning or not shutting down correctly.
  5. Examine for Water Intrusion: Check common areas for water leaks, such as under the carpet, in the spare tire well, or near electronic modules. Water damage can wreak havoc on electrical systems.

Common Causes for Electrical Issues & Battery Drain:

  • Failing alternator (not charging the battery adequately).
  • Parasitic draw from a malfunctioning module (e.g., infotainment, telematics, climate control) not entering sleep mode.
  • Faulty wiring or corroded/loose ground connections.
  • A failing battery, despite a 'good' test (sometimes a battery can test good but have insufficient cold-cranking amps or internal shorts).
  • Software glitches in various control modules.

When to See a Shop:

  • If you're unable to locate the source of a parasitic draw after pulling fuses.
  • If the alternator is found to be faulty, as replacement can be complex.
  • If you have persistent U-codes or B-codes that indicate module failures or communication issues.
  • For advanced diagnostics, as a professional shop can use specialized tools to monitor module activity and pinpoint the exact source of the problem, often intermittent, electrical problems.
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