Digital Bunn coffee maker displays E02 and stops brewing; unit may fill but does not heat properly.

Safety: Unplug the brewer and allow it to cool completely before removing covers. Internal tank water can be near boiling.

Steps:

• 1. Power cycle: Unplug for 5 minutes, plug back in, and attempt a brew. If E02 reappears, proceed.
• 2. Locate thermistor: Remove the top or rear cover. On many Bunn digital models, the thermistor is clipped or bolted to the side of the stainless hot water tank with two small wires leading to the control board.
• 3. Inspect wiring: Check the thermistor harness for cuts, melted insulation, or pulled connectors. Reseat the connector at the control board and at the thermistor if it is removable.
• 4. Test thermistor: With the unit unplugged, disconnect the thermistor and measure its resistance. Compare to Bunn service documentation (commonly 10–100 kΩ depending on temperature). An open circuit or 0 Ω indicates a failed sensor.
• 5. Check for corrosion: Look for green/white corrosion on the connector pins. Clean gently with contact cleaner and reconnect.
• 6. Replace as needed: If resistance is out of spec or intermittent when you gently wiggle the leads, replace the thermistor assembly. If a known-good thermistor still gives E02, the control board temperature input circuit is likely defective and the board should be replaced.

Note: Accurate temperature sensing is critical for brew quality and safety; do not bypass the thermistor.