What does error code E2 mean on a Google Nest thermostat?

No power wires detected. No power wires were detected. An Rc or Rh wire is required.

Can I fix Google Nest code E2 myself?

Start with these safe checks: Make sure the HVAC power is on. With power off, check that the R wire is fully inserted and the button stays down. If wiring looks right and the code stays, contact a pro.

When should I call a technician for code E2?

If wiring looks right and the code stays, contact a pro. Thermostat wiring is low voltage, but switch the HVAC system off at its breaker or service switch before pulling the thermostat off the wall. If the code points to the furnace or outdoor unit, leave gas, combustion and refrigerant parts to a licensed HVAC technician.

Google Nest Thermostat Error Code E2 / E22 / E72: No power wires…

What E2 means

No power wires were detected. An Rc or Rh wire is required.

Also shown as: E22, E72, E402, depending on the model.

Likely causes

Rc/Rh wire not inserted
HVAC power off

Safe first checks

Make sure the HVAC power is on.
With power off, check that the R wire is fully inserted and the button stays down.

When to stop

If wiring looks right and the code stays, contact a pro.

Checked against: Google Nest Help: Troubleshoot Nest thermostat help codes. Codes can differ by model and year, so confirm with your owner's manual.