HVACopediaLennox · Furnace
E203 Unit capacity not programmed
What the control is telling you
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)
Likely causes
- Replacement control not programmed
- Invalid unit code
Test and repair steps
- Make sure the control is idle (no heat, cool or fan) and set the room thermostat to OFF.
- Hold the diagnostic button until a solid P appears, then release; P starts blinking.
- Press and hold again; the control shows each unit size code for 3 seconds. Release on the correct code: 0=045V36B, 1=070V36B, 2=090V36C, 3=090V48C, 4=090V60C, 5=110V48C, 6=110V60C, 7=135V60D.
- While the selected code flashes (10 seconds), press and hold for 5 seconds; the control stores it and resets.
- If the 10 seconds run out or the button is held less than 5 seconds, nothing is saved; repeat.
- Cycle 24 V power to verify: the display should show the unit size code at power-up; three bars means it is still not recognized.
- Field replacement controls may need this manual configuration.
Settings for these units
Recommended filter size by cabinet width · EL296UHV
| Cabinet width | Side return | Bottom return |
|---|---|---|
| 17-1/2 in. | 16 x 25 x 1 in. (1) | 16 x 25 x 1 in. (1) |
| 21 in. | 16 x 25 x 1 in. (1) | 20 x 25 x 1 in. (1) |
| 24-1/2 in. | 16 x 25 x 1 in. (2) | 24 x 25 x 1 in. (1) |
Number in brackets is the quantity of filters.
Filters are field supplied and installed outside the furnace; inspect monthly.
Recommended filter size by cabinet width · Lennox SL280UHV
| Cabinet width | Side return | Bottom return |
|---|---|---|
| 14-1/2 in. | 16 x 25 x 1 in. (1) | 14 x 25 x 1 in. (1) |
| 17-1/2 in. | 16 x 25 x 1 in. (1) | 16 x 25 x 1 in. (1) |
| 21 in. | 16 x 25 x 1 in. (1) | 20 x 25 x 1 in. (1) |
| 24-1/2 in. | 16 x 25 x 1 in. (2) | 24 x 25 x 1 in. (1) |
Number in brackets is filter quantity; filters are field supplied.
Never run the unit without a filter installed.
- Filter sizes by cabinet width · Lennox SL297NV
Models that show this code
22 models in EL296UHV, Lennox SL280UHV, Lennox SL297NV
Other codes on the same units
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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. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.