Goodman communicating thermostat or control shows d0 and system does not respond to commands

Safety first: Turn off power to both indoor and outdoor units at breakers and disconnects. Low-voltage circuits can still be damaged by shorts.

Steps to check:

• 1. Inspect low-voltage cable: Follow the thermostat/control cable from the indoor unit to the Goodman condenser. Look for cuts, splices, or rodent damage.
• 2. Check connections at indoor board: Remove the blower door and locate the R, C, Y, Y2, and other terminals. Ensure the condenser control wires are firmly attached and not shorting to the cabinet.
• 3. Check connections at outdoor unit: In the condenser control compartment, verify the low-voltage wires from the indoor unit are secure on the contactor coil or control board terminals.
• 4. Inspect low-voltage fuse: On many Goodman indoor boards, a 3–5A automotive-style fuse protects the 24V circuit. If blown, replace with the same rating after correcting any shorts.

When to call a professional: If wiring and fuse are good but d0 persists, the outdoor control board or communicating interface may be faulty and should be diagnosed by a technician.