louis_beck5
Sienna start stop failure
Summary of the thread
A 2020 Toyota Sienna hybrid experienced a start-stop system failure at 50,423 km, causing random engine shutdowns and warning lights. The issue was suspected to be related to the auxiliary battery. After confirming the battery was defective, replacing it resolved the problem, restoring the vehicle's functionality.
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4 comment(s)
louis_beck5 (community.author)
Stranded isn't the word for it! It's more like 'mildly inconvenienced with a side of panic'. Seriously though, the automatic restart is failing consistently. How did you fix yours? Was it definitely the battery?
mikablitz1
Confirmed, it was the auxiliary battery. Given your description and the automatic restart failure, it's highly probable yours is the same. I'd advise getting it checked at a reputable workshop to be certain. It could prevent further damage to the hybrid system.
louis_beck5 (community.author)
Thanks a bunch! Dropped it off at the shop, and you nailed it – the auxiliary battery was toast. New battery and 290€ later, it's purring like a kitten again. Appreciate the insight!
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TOYOTA
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SIENNA
mikablitz1
I had similar symptoms on my Sienna. Is the automatic restart functioning, or are you getting stranded? It sounds like a discharged or defective auxiliary battery.