Goodman Furnace Error Codes: What the Blinking LED Means and How to Fix It

How Goodman Furnace Diagnostic LEDs Work

Modern Goodman furnaces include a diagnostic LED indicator on the control board. When the furnace detects a fault, the LED blinks a specific pattern—a series of flashes followed by a pause—to indicate the fault code. You can read the code without any tools or disassembly. To access: look through the small window on the lower furnace panel or remove the lower access panel. The LED is typically on the control board. Read as: X flashes, pause, X flashes again—so 3 flashes with a pause between = code 3. The code chart is printed on the inside of your access panel door.

Steady ON / Steady OFF

Steady ON: Normal operation—no fault detected. Steady OFF: No power to control board. Check power switch, breaker, and the 3-amp fuse on the control board. A blown fuse is common after a voltage spike.

2 Flashes: System Lockout

The furnace attempted to ignite and failed too many times, locking itself out as a safety measure. Usually means ignition failure—bad hot surface igniter, gas supply issue, or flame sensor problem. Reset by turning the thermostat off and back on or cycling the power switch. If it locks out again, diagnose the underlying ignition problem rather than keep resetting. See our guide to Goodman furnace won't ignite: causes and fixes.

3 Flashes: Pressure Switch Stuck Open

The pressure switch monitors draft airflow. Stuck-open means the furnace thinks there's inadequate draft. Most common causes: clogged condensate drain (very common in 90%+ units—water backup blocks the pressure port), blocked flue or intake PVC, failed inducer motor, or faulty pressure switch. In Minnesota winters, check PVC intake pipes for ice blockage first. See our guide to furnace pressure switch: what it does and how to fix it and condensate drain issues.

4 Flashes: Open High-Limit Switch

The high-limit switch shut the furnace down due to excessive heat—a safety protection. Most common cause: clogged filter is the #1 reason. Also: blocked vents, failed blower motor, undersized ductwork. Fix: replace the air filter immediately and open any closed vents. If it trips again after filter replacement, check blower motor operation. Persistent high-limit trips can crack the heat exchanger—see our guide to cracked heat exchangers.

5 Flashes: Flame Sensed Without Demand

The flame sensor is detecting flame when there's no call for heat. Usually a faulty flame sensor or control board. Requires professional diagnosis.

6 Flashes: Pressure Switch Stuck Closed

The pressure switch shows "closed" before the inducer motor starts—which shouldn't be possible. Usually a faulty pressure switch that needs replacement. Requires tech diagnosis.

7 Flashes: Low Flame Sense Signal

The furnace ignites but the flame sensor isn't reading strongly enough, causing shutdown shortly after ignition. Most common fix: clean the flame sensor rod with fine steel wool or emery cloth—an oxide coating insulates it over time. A $5 DIY fix. If cleaning doesn't resolve it, replace the sensor.

8 Flashes: Igniter Fault

The hot surface igniter (HSI) failed or is out of spec. HSI elements last 5-10 years and can fail suddenly. Replacement is typically $80-$200 parts and labor. See our guide on Goodman furnace ignition problems.

9 Flashes: Rollout Switch Open

A rollout switch tripped—flames escaped outside the burner compartment. This is a serious condition. Causes include cracked heat exchanger, blocked burner, or failed combustion air blower. Do not simply reset the rollout switch. Have the furnace inspected before restarting. Call a technician immediately.

Resetting a Locked-Out Furnace

For most lockouts: set the thermostat to OFF, wait 30 seconds, set back to HEAT. Or cycle the furnace power switch. If it locks out again within a few cycles, stop resetting and diagnose the underlying problem.

DIY vs. Tech

You can safely handle: replacing air filters, clearing a clogged condensate drain, checking for ice-blocked PVC pipes, cleaning a flame sensor, resetting a high-limit after filter replacement. Call a technician for: gas valve issues, cracked heat exchangers, rollout switches, failed igniters, persistent pressure switch faults, and any code you can't resolve with basic checks.

Preventing Error Codes

Most Goodman error codes are preventable through annual maintenance: burner cleaning (ignition issues), filter changes (high-limit trips), condensate drain cleaning (pressure switch faults), flame sensor inspection. A $80-$150 tune-up prevents most codes. Related: DIY furnace maintenance checklist | Furnace tune-up cost in Minnesota

If your Goodman furnace has persistent issues beyond maintenance, it may be time for replacement. Browse our factory-direct Goodman inventory with same-day Minneapolis/St. Paul delivery.