Goodman GMVC960803BN Error Code EC2: E-Module Network Communication Alarm
What Does Code EC2 Mean?
The Goodman GMVC960803BN can be paired with an external E-Module, an optional expansion device that plugs into the ComfortNet network to add control and integration capability beyond what the furnace's own Integrated Control Module provides. Code EC2 reports that the furnace board can no longer talk to that E-Module over the network.
This code is only meaningful on systems where an E-Module was actually installed. If your system does not use one, EC2 generally points to a configuration or wiring issue rather than a real device failure. Where an E-Module is present, EC2 means the features that module coordinates are temporarily offline while communication is down.
EC2 is low severity because it concerns an accessory control module, not the furnace's ability to make heat. The furnace continues to run and respond to heat calls; what is affected is whatever expanded functionality the E-Module was providing to the ComfortNet system.
Unlike EC1, which is about the primary furnace-to-thermostat link, EC2 is specifically the loss of the external E-Module. It also differs from EC3 (the Bluetooth module), EC4 (an equipment relay module), and EC5 (an accessory relay module). Typical causes are a disconnected or damaged data connection to the E-Module, loss of power to the module, or a failed module.
What You'll Notice
- EC2 appears on the furnace's 7-segment LED display while heating continues to work normally
- Features or integrations that the E-Module provided stop responding
- The ComfortNet thermostat may flag that an expected network device is missing or not responding
- The condition clears on its own once the E-Module is reconnected and communicating
- No change in basic heat output — burners and blower still respond to thermostat calls
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Lost communication with external E-Module | Most common | ✗ Call a pro → |
| E-Module wiring disconnected or faulty | Common | ✗ Call a pro → |
How This Is Diagnosed
A technician first confirms whether an E-Module is actually part of the system, since EC2 on a furnace with no E-Module usually indicates a configuration problem. If a module is installed, they check that it has power, inspect the data connection between the E-Module and the furnace control board for loose or damaged wiring, and verify the module is recognized on the ComfortNet network. If wiring and power are good but EC2 persists, the E-Module itself is the likely fault.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- An E-Module is installed and EC2 persists after the connections have been checked — the module may need to be replaced
- EC2 appears but no E-Module was ever installed, which suggests a network configuration issue to correct
- The functionality the E-Module was providing to the system does not return
- The data connection or power wiring to the E-Module shows visible damage or looseness
Frequently Asked Questions
What is an E-Module?
It is an optional external expansion module that plugs into the ComfortNet network to add control and integration features beyond the furnace's built-in control board. Not every system has one.
Will my furnace still heat with EC2 active?
Yes. EC2 concerns an accessory control module, not the furnace's core heating. Burners and blower keep responding to the thermostat; only the E-Module's added features are affected.
Why would EC2 appear if I don't have an E-Module?
In that case EC2 usually reflects a network configuration expecting a module that isn't there, rather than a real device failure. A technician can adjust the setup so the system stops looking for it.
✓ Verified against manufacturer service manual — March 2026