Lennox Error Code E203: Unit capacity not programmed (Furnace)
Lennox error code E203 on a furnace means: Unit capacity not programmed. It is also called Lennox diagnostic code E203.
Homeowner? What Lennox code E203 means for you
Stop and call Your furnace is reporting: Unit capacity not programmed. This code is a safety shutdown. Turn the furnace off and call a licensed technician. Do not keep resetting it. If you smell gas, leave the house and call your gas utility or 911 from outside.
Safe things you can check yourself
- Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
- Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does Lennox error code E203 mean?
No valid unit size (capacity) code is programmed; at power-up the display shows three horizontal bars followed by continuous E203. Critical alert.
Applies to: EL296UHV(X) series furnaces (integrated control 103130-XX and 107045-XX)
Common causes of Lennox code E203
- Replacement control not programmed
- Invalid unit code
Lennox models that use code E203
Show all 22 models
EL296UH045XV36BEL296UH070XV36BEL296UH090XV36CEL296UH090XV48CEL296UH090XV60CEL296UH110XV48CEL296UH110XV60CEL296UH135XV60DSL280UH060NV36ASL280UH070V36ASL280UH080NV48BSL280UH080NV60CSL280UH090V36BSL280UH090V48BSL280UH090V60CSL280UH100NV60CSL280UH110V60CSL280UH135V60DSL297UH040NV36BSL297UH060NV36BSL297UH080NV48CSL297UH080NV60C
Other Lennox Furnace codes
All Lennox Furnace error codes →
Lennox code E203: homeowner questions
What does Lennox code E203 mean?
Unit capacity not programmed. No valid unit size (capacity) code is programmed; at power-up the display shows three horizontal bars followed by continuous E203. Critical alert.
Is it safe to keep using my furnace with code E203?
No. Code E203 is a safety shutdown, so keep the furnace off until a licensed technician has checked it.
Can I reset Lennox code E203 myself?
Do not keep resetting it. Repeated resets can hide a safety problem; a licensed technician needs to find the cause.
Who can fix Lennox code E203 near me?
Aurora Star Tech Inc. repairs Lennox furnaces in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: Furnace Not Turning On: What to Check · Furnace Blinking Light: What the Flash Codes Mean
Troubleshooting guides
- Blowing cold air All brands · Furnace
- No heat All brands · Furnace
- Short cycling All brands · Furnace
- Blower motor does not run - Lennox SL280UHV ECM checks Lennox · Furnace
- Display shows two horizontal bars (soft disable) - Lennox SL297NV Lennox · Furnace
- Furnace will not run (no heat) - Lennox EL195UHNE Lennox · Furnace
- Furnace will not run (no heat) - Lennox SL297NV Lennox · Furnace
- Furnace will not run - Lennox SL280UHV checklist Lennox · Furnace
- Indoor blower does not run - Lennox EL195UHNE Lennox · Furnace
- Indoor blower does not run - Lennox ML180UHE Lennox · Furnace
- Poor ignition or combustion resonance - Lennox EL195UHNE Lennox · Furnace
- Poor ignition or loud combustion resonance - Lennox SL280UHNV Lennox · Furnace
- Two horizontal lines on display (soft disable) - Lennox communicating Lennox · Furnace
Source: Lennox EL296UHV(X) Unit Information / Service Literature, Table 5 Ignition Control 103130-XX Diagnostic Codes, p.34; Ignition Control 107045-XX Diagnostic Codes table, p.41, Program Unit Capacity Size Mode p.109. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.