9
High-heat pressure switch or relay did not close or reopened
This code typically points to
- Control relay defective
- Gas valve miswired
- Low-heat proving issues carried forward from code 3
Next checks to confirm
- Check high-fire proving path and refer to code 3 chain
Escalation
Escalate to control relay or high-stage proving circuit if low-stage proves normally.
Reset behavior
Clears when proving path is restored.
Urgent
Fix now