Goodman GMVM970803BN Error Code E9: High Stage Pressure Switch Stuck Open
What Does Code E9 Mean?
An E9 code on the Goodman GMVM970803BN means the high stage pressure switch failed to close after the induced draft blower was energized, so the Integrated Control Module cannot confirm that venting is adequate for high-fire operation. On this modulating, variable-speed furnace the inducer runs faster to pull more draft when the furnace steps up to high stage, and the high stage pressure switch is the safety device that proves that extra draft actually exists. When that switch does not close, the board holds the furnace on low stage rather than firing at full capacity.
E9 is the high-stage counterpart of the E2 code, which reports the low stage pressure switch failing to close. The high stage switch is set to trip at a greater negative pressure than the low stage switch, so a venting restriction can be mild enough to let the low stage switch close (low fire still works) while starving the high stage switch of the pressure it needs. That is why E9 typically leaves you with heat but only at reduced output, and why this model rates it as a low-severity fault rather than a full lockout like E2's stuck-open condition would suggest for the low stage.
Because the failure is about airflow and pressure rather than the switch alone, the causes mirror E2: a pressure switch hose that is cracked, pinched, or holding water; a partially blocked flue or intake pipe; a clogged condensate drain raising backpressure; or an induced draft blower that cannot spin up enough for high-stage draft. E9 differs from E8, which is the same switch found already closed before the cycle even starts; E9 is the switch failing to close under draft. The ECM communicating blower will run at its low-stage airflow while this condition persists.
What You'll Notice
- The furnace runs and makes heat, but only at low fire — it never reaches full output
- The induced draft blower is clearly running, yet the furnace still will not step up to high stage
- The home warms slowly and may fall behind the thermostat setpoint during a cold snap
- The dual 7-segment display shows E9
- Symptoms may worsen after the furnace has sat idle over summer, when nests, ice, or debris can partially block the vent or intake
Common Causes
How This Is Diagnosed
A technician works from the airflow path inward before condemning the switch. They inspect the pressure switch hose for cracks, kinks, or trapped moisture, then verify the flue and intake pipes are clear, correctly sized, and properly terminated, and check the condensate drain for a blockage that could raise backpressure. Using a manometer, they measure the actual negative pressure at the high stage switch tap while the inducer is at its high-stage speed and compare it to the switch's rated set point.
That pressure reading is the deciding step: if the draft is below the set point, the problem is a venting restriction or a weak induced draft blower, not the switch; if the draft is adequate but the switch still will not close, the switch itself is failed. Any replacement pressure switch or induced draft blower must be the correct model-specific part so the set point and airflow characteristics match the furnace's design.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The furnace runs on low fire only and shows E9, and basic checks of the outdoor vent and intake terminals for nests, ice, or debris have not restored high stage
- E9 appears seasonally or intermittently, suggesting a partial vent restriction or a hose holding moisture that needs measurement to pin down
- The condensate drain or pressure switch hose is suspected of blockage and needs to be cleared and verified with a manometer
- The high stage pressure switch or induced draft blower is confirmed faulty and needs replacement with the correct part
Frequently Asked Questions
Why will my furnace only run on low stage with an E9?
The high stage pressure switch is not closing, so the control board cannot prove there is enough venting draft for full-fire operation. It keeps the furnace on low stage, where the separate low stage switch is still closing normally, so you still get heat but not full capacity.
Is E9 the same as E2?
They are the same type of fault — a pressure switch that will not close — but E2 is the low stage switch and E9 is the high stage switch. E9 usually still leaves you with low-stage heat, whereas an E2 stuck-open condition stops normal operation.
Can a dirty vent cause an E9?
Yes. A partial blockage in the flue or intake, a nest or ice at the outdoor terminal, or a clogged condensate drain can reduce draft just enough that the higher-set high stage switch cannot close, even while low stage still works.
How urgent is an E9 repair?
It is a low-severity code and the furnace keeps heating on low stage, so it is not an emergency, but you should have it checked before the coldest weather since a venting restriction can worsen over time. Repair costs vary by region and by whether the fix is a cleared vent, a hose, or a replaced part.
✓ Verified against manufacturer service manual — March 2026