On the covered Google Nest thermostat, E257, E258, E294 means the wires were not configured properly in the Google Home app. Google words them as: heat pump requires Y1 wire (E257), W2 wire requires W1 (E258) and R wire is required (E294). First, look at whether the thermostat display shows a link such as g.co/nest/needWY, which tells you which wire to check.
Differential
Likely causes of “Google Nest thermostat code E257, E258, E294”, and how to tell them apart
- 1
A heat pump set up without a Y1 wire
What separates it E257 right after installation on a heat pump
How to confirm Compare the wiring screen in the app with the wires on the old thermostat photo
- 2
W2 entered without W1
What separates it E258 where a second-stage heat wire was added alone
How to confirm Check the app wiring page for W2 without W1
- 3
No R wire connected
What separates it E294 and the display stays dark or restarts
How to confirm Look for a power wire at R, Rc or Rh at the backplate
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether the thermostat is on a heat pump system
- The picture you took of the old wiring
- The letters on the terminals where each wire sits
- Which code shows
Try in this order
0 of 5 completedWhat to do first
ReversibleLook at whether the thermostat display shows a link such as g.co/nest/needWY, which tells you which wire to check.
Correct only the documented fault domain
ReversibleGoogle's fix: reset the thermostat to factory defaults, add it back to the Google Home app, and enter the wires again from a picture of the old thermostat, moving any wires so they match the app's wiring diagram. Make sure system power is off before moving a wire, that about 1/3 to 1/2 inch of copper is showing, and that the connector button stays down.
Read the link on the display
ReversibleGoogle's display shows a link such as g.co/nest/needWY that names the missing wire.
Reset the thermostat to factory defaults
ReversibleReset it, then add it back in the Google Home app and enter the wires again from the picture of the old thermostat.
Move wires to match the app
ReversibleWith power off, move any wire so it agrees with the wiring diagram in the app, with about a third to a half inch of bare copper inserted.
Model-specific
What is true of this model and not of its siblings
- Shown as
- E257, E258 or E294 with a help link.
- Applies to
- Google Nest thermostats.
Stop boundary
When this stops being a self-service repair
- !Turn system power off at the breaker before moving any wire
- !Call an HVAC technician if you cannot identify the wires or the system has no R wire
Evidence ledger
Sources behind this answer
Exact questions
Common questions
What does E257, E258, E294 mean on a Google Nest thermostat?+
The wires were not configured properly in the Google Home app. Google words them as: heat pump requires Y1 wire (E257), W2 wire requires W1 (E258) and R wire is required (E294).
Do I need a C wire?+
A common wire helps stable power, but these three codes are about the Y1, W1 and R settings.
Will resetting lose my schedule?+
A factory reset clears the thermostat's settings, so you set it up again in the app.