NHTSA Complaint #11666612 — 2021 SUBARU FORESTER

My vehicle is equipped with automatic start/stop system. In early 2024, I began having issues with sluggish restart during the start/stop cycle. I took it into the dealer at that time, who stated it required a software update and charged the battery. The issue persisted. It was more serious, as it was not just sluggish on the restart, but the restart would fail and stall the car. This happened in heavy traffic, which was very scary and unsafe. I took the vehicle back into the dealer in late 2024 for the same issue. They did another software update and charged the battery again. They recommended that we purchase a new battery. One month later, we purchased an upgraded AGM battery, as it was recommended for auto start/stop systems. The issue continued to persist. First, with sluggish restart. Later, the auto start/stop system failed again in heavy traffic. We took the vehicle in again, and again the dealer stated it was the battery. They recommended we purchase a new battery. It was explained the battery was 6 months old, and the issue has never been fixed. Further, it was pointed out that the car could be restarted manually with the push button ignition, after a start/stop system failure. That led us to believe it was not a battery failure, but a deeper system failure. The dealer continues to assert it is the battery, even though it happened with a factory battery and a new, upgraded, battery. Neither of the batteries have failed testing, and report as "good" on the diagnosis forms. We believe there is a system issue, that is causing issues with the auto start/stop system, and is not being identified by the dealer. It is a safety issue, as it has happened in heavy traffic several times. We have attached diagnostic reports from March 2024 and June 2025, but cannot find the October 2024 diagnostic report.