Bryant 355MAV Error Code 25: Model Selection or Setup Error
What Does Code 25 Mean?
Status code 25 on the Bryant 355MAV indicates a configuration error on the control board. Either the model plug (PL4) is missing or installed incorrectly, or setup switches SW1-1 or SW1-6 on the control board are in the wrong position. These configuration settings tell the control board which specific furnace model it is installed in and how to operate it.
The model plug is a small resistor plug that plugs into the PL4 connector on the control board. Each furnace model has a specific plug with a specific resistance value that identifies the model. If the plug is missing, the wrong plug is installed, or the connector is loose, the board cannot properly configure itself. If the code only flashes 4 times on power-up, the control is falling back to model settings stored in memory, which may work temporarily.
This code most commonly appears after a control board replacement when the installer forgets to transfer the model plug from the old board or installs the wrong one. It can also occur if a setup switch is accidentally bumped during service work. An HVAC technician can resolve this by verifying the correct model plug and switch positions using the furnace's wiring diagram.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Model plug (PL4) missing or incorrect | Most common | ✗ Call a pro → |
| Setup switch SW1-1 or SW1-6 positioned improperly | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace shows code 25 — a technician needs to check the model plug (PL4) and setup switch positions
- The code appeared after a control board replacement or service work
✓ Verified against manufacturer service manual — March 2026