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info Honeywell
Status PnG
Ping mode for verifying communication with non-battery powered devices.
? What Causes This
User entered SERVICE MODE to test device communication.
ⓘ What This Means
Select PnG using UP/DOWN arrows, press MODE, select target device address, and press FAN to start pinging. Press FC to stop.
Source: page 38 of the official manual
From the manual
This error code appears in:
Honeywell Thermostat Battery