Goodman GMVM970803BN Error Code E1: Low Stage Pressure Switch Stuck Closed

What Does Code E1 Mean?

An E1 code on the Goodman GMVM970803BN indicates the low-stage pressure switch is stuck in the closed position before the heating cycle has even begun. This switch is a safety device that monitors draft through the heat exchanger and venting system. On this modulating furnace the board expects the switch to be open (its default, unpressurized state) at the start of every call for heat, because that is how it proves the switch can actually respond to inducer draft. If it finds the switch already closed, it cannot verify that the safety circuit is working, so it refuses to start.

This is the mirror image of the E2 fault on the same board. E1 is the switch stuck CLOSED before the inducer runs; E2 is the low-stage switch failing to close (stuck open) after the inducer runs. Both involve the same low-stage switch, but they fail the board's check at opposite ends of the sequence, and they usually have different root causes — E1 points at the switch or its wiring, while E2 points more often at venting and draft.

E1 most commonly occurs when the pressure switch contacts have become mechanically stuck or welded together, or when there is an electrical short in the wiring between the switch and the Integrated Control Module that makes the circuit read closed even when the switch is not. In either case the board cannot trust the low-stage venting signal and will not proceed. A ComfortNet thermostat shows "Call for Service" and scrolls "Check Furnace" while the code is active. This is not a DIY-serviceable condition — confirming it requires electrical testing of the switch and harness.

What You'll Notice

• The furnace will not start a heating cycle and the display shows E1
• A ComfortNet thermostat lights "Call for Service" and scrolls "Check Furnace"
• The failure happens right at the beginning of the call for heat, before ignition is attempted
• The problem persists across power cycles because the switch or wiring is physically shorted closed
• No warm air is produced even though nothing sounds obviously wrong at first

Common Causes

How This Is Diagnosed

Because E1 is a pre-start check failure, a technician goes straight to the low-stage pressure switch and its circuit. With power off, they meter the switch contacts to see whether they are physically stuck closed at rest, and inspect the wiring harness between the switch and the Integrated Control Module for a short, a pinched wire, or moisture that would make the circuit read closed.

If the switch tests stuck closed, it is replaced with the correct part matched to the original set point, since an incorrect switch can defeat the venting safety it is meant to prove. If the switch is good but the circuit still reads closed, the technician traces the harness for the short. They also check the pressure switch hose for standing water or debris that could influence the switch, before returning the furnace to service.

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 display shows E1 and the furnace never begins its ignition sequence
• The code is present the moment the thermostat calls for heat, before the inducer settles
• E1 persists after a power cycle, indicating a physically stuck switch or shorted wiring
• Wiring near the pressure switch looks pinched, chafed, wet, or damaged

✓ Verified against manufacturer service manual — March 2026