Thermostat shows E16 and indicates a firmware update failure; device may be stuck on an update screen.

Safety: Do not repeatedly cut power during an update unless the device is clearly frozen for an extended period.

• Wait first: Allow at least 15–20 minutes to ensure the update is not still processing in the background.
• Stable power and Wi‑Fi: Ensure the HVAC breaker is on and Wi‑Fi is stable. Avoid resetting your router during updates.
• Power cycle: If the thermostat is frozen, turn off power at the breaker for 1 minute, then restore. Check if it boots normally.
• Retry update: From the Bosch app or thermostat menu, check for updates again and re‑apply if offered.
• Contact Bosch support: If E16 persists and the thermostat will not boot normally, it may require replacement under warranty.