2 blinks
Pressure switch circuit open
This code typically points to
- Inducer draft insufficient
- Blocked pressure-switch tubing or inducer port
- Blocked or restricted vent
- Blocked heat exchanger
- Intermittent pressure-switch operation
- Water/moisture in hoses
Next checks to confirm
- Check negative pressure with Magnehelic
- Inspect pressure-switch tube/port
- Inspect venting
- Inspect hoses and switch contacts
- Inspect heat exchanger restriction if indicated
Escalation
Fault indication; on related later boards, prolonged proving failure becomes timed soft lockout
Reset behavior
Clears when pressure-switch circuit proves normally.
Urgent
Fix now