Google Nest thermostat code E109, E110, E111, E112, E113 and E439 to E443: meaning and exact next steps
E109, E110, E111, E112, E113 and E439 to E443 means The thermostat detects a conflict involving the G (fan) wires. Google words them as: G2 detected and G1 also required (E109, E439); G2 detected, remove the W2/AUX wire (E110, E440); G2 detected, remove the E wire (E111); G or G3 detected and G1 and G2 also required (E112, E442); G2 and O/B conflict (E113, E443). This answer applies only to Google Nest Learning Thermostats (1st through 4th generation), the Nest Thermostat E and the Nest Thermostat that show a lettered help code on the display or in the Nest or Google Home app. Google prints one meaning for the aliases it groups together, and this page keeps that grouping. Codes shown by other brands of thermostat are on their own pages.
On the covered Google Nest thermostat, E109, E110, E111, E112, E113 and E439 to E443 means the thermostat detects a conflict involving the G (fan) wires. Google words them as: G2 detected and G1 also required (E109, E439); G2 detected, remove the W2/AUX wire (E110, E440); G2 detected, remove the E wire (E111); G or G3 detected and G1 and G2 also required (E112, E442); G2 and O/B conflict (E113, E443). First, photograph the thermostat wires and note which fan-related connectors (G, G1, G2, G3) hold a wire.
Common questions about “Google Nest thermostat code E109, E110, E111, E112, E113 and E439 to E443”
What does E109, E110, E111, E112, E113 and E439 to E443 mean on a Google Nest thermostat?+
The thermostat detects a conflict involving the G (fan) wires. Google words them as: G2 detected and G1 also required (E109, E439); G2 detected, remove the W2/AUX wire (E110, E440); G2 detected, remove the E wire (E111); G or G3 detected and G1 and G2 also required (E112, E442); G2 and O/B conflict (E113, E443).