Modern Goodman furnaces have an LED diagnostic light on the control board that flashes error codes when a fault is detected. These codes are your furnace's way of telling you exactly what's wrong — or what tripped the safety system. Knowing how to read them can save you a service call for simple fixes, and help you describe the problem accurately when you do need a technician. Here's a comprehensive guide to Goodman fault codes.
How to Read the Diagnostic LED
The LED light on the Goodman control board blinks in a pattern: X flashes, pause, Y flashes. Count the flashes in each group to get the code (e.g., 3 flashes, pause, 1 flash = code 31). The code legend is printed on a sticker inside the furnace's front access panel. Most Goodman furnaces also display the last 5 fault codes in memory, accessible by pressing the diagnostic button.
Common Goodman Fault Codes and What They Mean
| Code | Meaning | Common Cause | Action |
|---|---|---|---|
| 11 | No previous fault code | Normal operation after power cycle | No action needed |
| 13 | Limit circuit fault — lockout | Clogged filter, blocked vent, dirty blower, high static pressure | Replace filter, check venting, check for blockages |
| 14 | Ignition lockout | Failed ignitor, dirty flame sensor, gas supply issue | Check gas supply, inspect ignitor and flame sensor |
| 21 | Gas heating lockout | Failed ignition repeatedly; gas valve or inducer issue | Service call — do not repeatedly reset |
| 22 | Abnormal flame-proving signal | Dirty or failed flame sensor; gas pressure issue | Clean flame sensor rod with steel wool |
| 23 | Pressure switch stuck open | Blocked condensate drain, cracked inducer housing, kinked pressure switch tubing | Check condensate drain; inspect inducer |
| 24 | Secondary voltage fuse blown | Short circuit in thermostat wiring or control board | Inspect thermostat wiring; service call if wiring is intact |
| 31 | High limit device fault | Restricted airflow (clogged filter), blocked registers, dirty blower wheel | Replace filter, open all registers, check blower |
| 33 | Limit circuit fault | Same as code 13/31 — high limit tripped due to airflow restriction | Replace filter immediately; check all supply and return registers |
| 34 | Ignition proving fault | Flame sensor dirty or failed; weak gas pressure | Clean flame sensor; check gas pressure |
| 41 | Inducer motor fault | Failed inducer motor; wiring fault at inducer | Service call — inducer motor replacement |
| 43 | Draft safeguard fault | Blocked exhaust pipe, inducer fault, pressure switch issue | Check PVC exhaust for blockage; service call if clear |
| 45 | Control board fault | Failed control board | Service call — control board replacement |
Most Common DIY-Fixable Faults
Code 13/31/33: High Limit Fault (Clogged Filter)
The high-limit switch is a safety device that shuts the furnace down if the heat exchanger gets too hot. The most common cause is a clogged air filter blocking airflow. Fix: replace the filter, wait 30 minutes for the furnace to cool, then reset the thermostat. If it trips again within a few hours, the blower wheel may be dirty or registers may be blocked.
Code 22/34: Flame Sensor Issue
The flame sensor rod gets coated with oxidation over time and can't reliably detect the burner flame. The furnace starts, the burner ignites, but the sensor doesn't "see" the flame and shuts down. Fix: remove the flame sensor rod (one screw), gently rub the rod with fine steel wool or emery cloth, reinstall. This often resolves repeated ignition failures with no parts cost.
Code 23: Pressure Switch Stuck Open
Pressure switches confirm that the inducer motor is creating proper draft. A stuck-open pressure switch is often caused by a clogged condensate drain — when the drain backs up, water gets into the pressure switch tubing and prevents it from closing. Fix: clear the condensate drain, drain the trap, and retry.
When to Call for Service
Call a technician for codes 21, 41, 45, or any code that returns immediately after resetting. Also call for code 14 (ignition lockout) if cleaning the flame sensor doesn't resolve it — the ignitor itself may need replacement.
How do I read a Goodman furnace error code?
The LED light on the control board blinks in groups. Count the flashes before each pause — the pattern forms a two-digit code. The code legend is on a sticker inside the furnace door panel. For example, 3 flashes, pause, 1 flash = code 31 (high limit fault).
What does Goodman error code 13 mean?
Code 13 indicates a limit circuit fault — the furnace shut down because the heat exchanger overheated. The most common cause is a clogged air filter restricting airflow. Replace the filter, let the furnace cool 30 minutes, and reset.
How do I fix a Goodman furnace flame sensor issue (code 22 or 34)?
Remove the flame sensor rod (one screw), lightly rub the metal rod with fine steel wool or emery cloth to remove oxidation, and reinstall. This often resolves repeated ignition failures at no cost. If the problem persists after cleaning, the sensor may need replacement ($20–$50 part).
What causes a Goodman pressure switch fault (code 23)?
Code 23 most commonly results from a clogged condensate drain backing water into the pressure switch hose, preventing the switch from closing. Check and clear the condensate drain line. A cracked inducer housing or failed inducer motor can also trigger this code.
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