A. O. Smith · Voltex hybrid with letter codes (HPTU, 2016–2019)
A. O. Smith Voltex hybrid with letter codes (HPTU, 2016–2019) error code E40 or E41
Discharge temperature sensor
What it means
Heat Pump Discharge Temperature Sensor is not functioning.
What A. O. Smith says to do
These steps involve electrical testing or parts replacement. A. O. Smith's manuals tell owners to leave that work to a qualified service technician.
Power off (Power Cycling the unit), disconnect and reconnect J2 and J5 connections from control board, inspect wire for damage, re-install UIM, reconnect power. If error persists, replace temperature sensor.
Last checked 2026-10-03.
Safety first
- WARNING! Electric Shock Hazard; Disconnect power before servicing. Do not remove the plastic guard from over wiring. Do not touch electrical wiring. Failure to do so can result in death or electrical shock. (diagnostic code pages, p.20-21)
- WARNING! Working near an energized circuit can result in severe injury or death from electrical shock. WARNING! When you are finished, be sure all covers are secured to reduce the risk of fire and electric shock. (p.22)
From the manufacturer's manual for this series.
The same code on other models
Codes mean different things on different heaters. Match the series to the model number on your rating label.
- A. O. Smith Early Voltex hybrid (FPTU, 2015 manual): E40 or E41
- Whirlpool Hybrid HPSE2K50/66/80: E40 or E41
Other Voltex hybrid with letter codes (HPTU, 2016–2019) codes
- - / -- / --- (System diagnostic)
- ICE (Defrost)
- HPO (Out of operating range)
- EUC (Upper element)
- ELC (Lower element)
- SF (Air filter)
- ECF (Compressor short cycling)
- E20 or E21 (Upper temperature sensor)
- E30 or E31 (Lower temperature sensor)
- E50 or E51 (Suction temperature sensor)
- E10 or E11 (Coil temperature sensor)
- E60 (Upper and lower sensors)
- Edr (Dry fire / tank not full)
- EPL (Low supply voltage)
- EDH (Discharge temperature high)
- EoF (Condensate management)
- ECL (Suction pressure low)
- EEE (EEPROM failure)
- ECC (Compressor not functioning)
- ECE (Power supply error)