2019 Audi S4 — battery dies after the car sits for a weekend

I went back under the 2019 Audi S4 and it only happens after a heat soak, not on a cold start. I refuse to clear codes until someone else sees them.

Start with the test that can prove you wrong. A pressure test beats staring at a dry driveway if the 2019 Audi S4 is losing coolant with no puddle. Save the big job until that test fails. If it doesn't change the out-the-door or the repair estimate, it's noise. If that fails I'll eat the diagnostic fee.

It did battery dies after the car sits for twice this week, both times after sitting. No change in mileage feel. Wrote this up on my lunch break.

If it were in my driveway, move a coil or plug on the 2019 Audi S4 if it's cylinder-specific and see whether the code follows. If the cheap test changes it, stop and reassess. I'd want that in writing, not as a promise. I'd sleep better after that step, even if it finds nothing. If that fails I'll eat the diagnostic fee.

Log the conditions before you spend. If a shop can't duplicate it on the 2019 Audi S4, bring a video plus freeze-frame data, not just a story. You'll know quickly if you're on the wrong tree. On “battery dies after the car sits for,” that was the fork that mattered for me. This is from a 2019 Audi S4 in Austin with 86,000 miles. Write the result down so the next test isn't a repeat of the last one. I'd rather pay for diagnosis than a second guess-repair.

This is usually cheaper to test than to guess. Get a real battery/charging test on the 2019 Audi S4, not just resting voltage, before blaming a module. If the cheap test changes it, stop and reassess. Run the total, not the monthly, before you commit. That's coming from doing this as an owner, not a shop. I'd rather look cautious in this thread than stuck later.

Ask what changed right before it started. Loaded-suspension checks on the 2019 Audi S4 catch play that a wheels-hanging inspection misses. That's the branch I'd chase this week. Keep sale price, fees, and rate as three different conversations. I'll update if anything new shows up.

Start with the test that can prove you wrong. Capture voltage while the 2019 Audi S4 is actually failing — after it restarts you've lost the clue. You'll know quickly if you're on the wrong tree. This is from a 2019 Audi S4 in Austin with 86,000 miles. Any freeze-frame data saved? Worth doing even if the car feels fine right now. Wrote this up on my lunch break.

Start with the test that can prove you wrong. Get a real battery/charging test on the 2019 Audi S4, not just resting voltage, before blaming a module. Don't erase codes until someone who can help has seen them. If you share a photo of the worksheet, easier to sanity-check. Wrote this up on my lunch break.

If it were in my driveway, a pressure test beats staring at a dry driveway if the 2019 Audi S4 is losing coolant with no puddle. That's the branch I'd chase this week. Happy to compare notes if your setup is different. Next check is the cheap one I can do in a driveway.

OP update: scanned the 2019 Audi S4 again and still only have the one pending code, no new lights. Doing the boring step first on purpose.

Ask what changed right before it started. Move a coil or plug on the 2019 Audi S4 if it's cylinder-specific and see whether the code follows. If the cheap test changes it, stop and reassess. I'd want a dollar figure or a measured spec, not 'should be fine.' If this is nothing, great. I want that in data.

Intermittent stuff lies if you only catch it once. Swap the cheap/easy piece first on the 2019 Audi S4 and see if the fault moves. If the cheap test changes it, stop and reassess. On “battery dies after the car sits for,” that was the fork that mattered for me. Was this after sitting overnight? Video is ugly but it shows the hesitation.

Intermittent stuff lies if you only catch it once. If a shop can't duplicate it on the 2019 Audi S4, bring a video plus freeze-frame data, not just a story. That's the branch I'd chase this week. On “battery dies after the car sits for,” that was the fork that mattered for me. Run the total, not the monthly, before you commit. Climate here is different, so treat that as a local data point. Not driving it hard until I know more.

I'd want a measurement, not a hunch. If a shop can't duplicate it on the 2019 Audi S4, bring a video plus freeze-frame data, not just a story. You'll know quickly if you're on the wrong tree. This is from a 2019 Audi S4 in Austin with 86,000 miles. I'd want that in writing, not as a promise. No warning lights, which is why I'm documenting it.

I wouldn't throw parts yet. Loaded-suspension checks on the 2019 Audi S4 catch play that a wheels-hanging inspection misses. That's the branch I'd chase this week. Did the worksheet show tax yet? Cold start is when I can actually reproduce it.