ICP Furnace Error Codes: Meaning, Troubleshooting, and Fixes

ICP furnace error codes help homeowners and technicians diagnose common heating problems quickly. This article explains the most frequent ICP error codes, what they indicate, and step-by-step troubleshooting and repair guidance that aligns with manufacturer practices. The information targets U.S. homeowners and service professionals who need concise, accurate diagnostics for ICP (International Comfort Products) and related brands.

Code	Common Meaning	Primary Action
01	No Flame / Ignition Failure	Check ignition control, gas supply, flame sensor
02	Pressure Switch Fault	Inspect venting, pressure switch tubing, inducer motor
03	Limit/High-Temperature Lockout	Clean heat exchanger, check airflow and limit switch
04	Blower Or Fan Fault	Test blower motor, capacitor, control board outputs

How ICP Furnace Error Codes Work

ICP furnace error codes are reported by the furnace control board using LED flashes, blinking displays, or alphanumeric readouts. Codes indicate specific safety or operational faults that the control board detects during startup and operation.

Key Point: Reading the code accurately and noting the furnace behavior (no flame, continuous lockout, or short cycles) is essential before troubleshooting.

Common ICP Error Codes And What They Mean

Error Code 01 — Ignition Or Flame Detection Failure

Error code 01 typically indicates that the furnace attempted to light but did not detect a flame. Causes include faulty ignitor or hot surface ignitor (HSI), dirty flame sensor, blocked gas valve, or ignition control failure.

Troubleshooting steps: inspect the ignitor for cracks, test flame sensor continuity and clean with fine steel wool, verify that the gas valve receives 24VAC during ignition, and observe the ignition sequence for timing abnormalities.

Error Code 02 — Pressure Switch Or Venting Problem

Error code 02 signals that the pressure switch did not close or open correctly. This is often caused by blocked venting, a stuck pressure switch, obstructed inducer motor or collapsed pressure tubing.

Troubleshooting steps: visually inspect vent termination for debris, test pressure switch with a multimeter, check tubing for kinks or water, and confirm the inducer motor runs and reaches expected vacuum levels.

Error Code 03 — High Limit Or Overtemperature Lockout

Error code 03 indicates that a high-limit switch or rollout sensor tripped, shutting the furnace down to prevent overheating. Common causes are restricted return airflow, dirty air filter, blocked ducts, or a malfunctioning limit switch.

Troubleshooting steps: replace or clean air filter, ensure returns and supply registers are open, inspect heat exchanger for soot or debris, and test the limit switch for proper operation.

Error Code 04 — Blower Motor Or Fan Failure

Error code 04 often refers to blower motor issues, failed fan relay, or problems with the blower capacitor. This can prevent proper airflow and cause system lockouts.

Troubleshooting steps: check blower motor continuity, measure capacitor microfarads if labeled, inspect control board blower output, and verify motor starts on calls for heat and cooling (if combined system).

Error Code 05 — Low Flame Signal Or Flame Loss During Operation

Error code 05 means the flame signal dropped below expected levels after initial ignition. Causes include a weak flame, wiring issues, dirty flame sensor, or intermittent gas pressure.

Troubleshooting steps: clean flame sensor, check wiring harness continuity to control board, monitor gas pressure during operation, and ensure manifold pressure matches specifications.

Other Codes And Indicators

ICP and related brands may display manufacturer-specific codes such as 10, 11, 12 for different sequences or LED blink patterns. Always consult the furnace’s data plate and manual for the precise code table since models vary.

Key Point: If the control board displays nonstandard codes or rapid blinking, reference the exact model’s service manual for interpretation.

Safety First: Preparations Before Troubleshooting

Always turn off power to the furnace at the service switch or breaker before inspecting internal components. Shut off the gas supply when testing or replacing gas-carrying components.

Wear safety glasses and gloves when accessing burners, the heat exchanger, or electrical terminals. If the furnace is under warranty or if the user is not comfortable with gas/electrical work, contacting a licensed HVAC technician is recommended.

Step-By-Step Diagnostic Checklist

1. Record the error code and observe furnace behavior during startup and shutdown.
2. Check basic items: thermostat settings, power to furnace, and gas supply.
3. Inspect and replace a clogged air filter to rule out airflow-related limit trips.
4. Listen for inducer motor operation and verify vent termination is clear.
5. Visually inspect the ignitor and flame sensor; clean or replace as needed.
6. Test pressure switch, blower motor, capacitors, and relays using a multimeter.
7. Verify control board LED patterns and consult the model-specific service manual.

Testing And Replacing Key Components

Ignitor And Flame Sensor

HSI ignitors are fragile; a visible crack or break means replacement. Flame sensors often fail due to oxidation; cleaning with fine emery or replacing when corroded restores reliable sensing.

Pressure Switch And Tubing

Pressure switches are inexpensive but require correct vacuum levels to change state. Use a manometer or vacuum gauge when precise measurement is necessary. Replace collapsed or brittle tubing to restore accurate pressure sensing.

Control Board Diagnostics

Control boards output specific voltages to sequence ignition, inducer and blower motors. Test for 24VAC and expected control outputs during calls for heat. Replace the board if outputs are missing or if the board shows burned traces or bulging capacitors.

Blower Motor And Capacitor

Measure motor windings for continuity and check the capacitor value against the motor nameplate. Intermittent blower operation often points to a failing capacitor or motor bearings rather than the board.

When To Call A Professional

Contact a licensed HVAC technician if troubleshooting requires gas valve replacement, brazing, heat exchanger repairs, or if the furnace displays persistent lockouts after basic repairs. Technicians can perform combustion analysis and in-depth electrical diagnostics safely.

Key Signs To Call A Pro: Visible cracks in the heat exchanger, persistent pressure switch faults after vent cleaning, gas-smell, or repeated flame rollout codes.

Preventive Maintenance To Reduce Error Codes

• Replace filters every 1–3 months depending on use and filter MERV rating.
• Keep vent terminations clear of vegetation, nests, and snow.
• Schedule annual professional tune-ups to inspect heat exchanger, burners, and controls.
• Clean flame sensors and burners during routine service to maintain reliable ignition and combustion.
• Maintain proper thermostat settings to avoid short cycling and strain on components.

Model-Specific Notes And Brand Relationships

ICP is a parent or OEM for several consumer brands such as Armstrong Air, Ducane, Heil, and Tempstar. Error code patterns and control boards can be shared across models, but the exact code meaning can vary by control board family.

Always lookup the specific model number on the furnace data plate and review its service manual for accurate code tables and wiring diagrams.

Cost Estimates For Common Repairs

Repair	Typical Cost Range (U.S.)
Ignitor Replacement	$80 – $220
Flame Sensor Clean/Replace	$40 – $140
Pressure Switch Replacement	$90 – $250
Blower Motor Or Capacitor	$150 – $650
Control Board Replacement	$200 – $900

Prices vary by region, model, and whether work is performed during emergency service hours. Always request a written estimate from the service provider.

Useful Tools And Equipment For DIY Diagnostics

• Digital multimeter for voltage and continuity checks.
• Manometer or vacuum gauge for pressure switch diagnosis.
• Small mirror and flashlight for burner and heat exchanger inspection.
• Replacement parts: ignitor, flame sensor, pressure tubing, and 24VAC relays.
• Manufacturer service manual or access to online technical bulletins.

Additional Resources And References

Reference the furnace data plate for model and serial numbers and consult ICP or brand-specific service literature for exact code definitions. Industry resources such as ACCA (Air Conditioning Contractors of America) and NATE-certified technician guides provide best practices for diagnostics and safety.

Key Resource Tip: Keep photos of the control board and wiring before disassembly to ensure correct reconnection.