Bryant 355MAV Error Code 25: Model Selection or Setup Error
What Does Code 25 Mean?
Status code 25 on the Bryant 355MAV is a configuration error, not a mechanical fault. Either the model plug (PL4) is missing or incorrect, or setup switches SW1-1 or SW1-6 on the control board are in the wrong position. These settings tell the Variable Speed Furnace Control which model it is running and how to stage the two-stage gas valve and variable-speed blower.
The model plug is a small resistor plug on the PL4 connector; each model uses a specific resistance value to identify itself to the board. If the plug is missing, wrong, or loose, the board cannot configure itself correctly. The manual notes that if the code flashes only 4 times on power-up, the control is falling back to the model selection stored in memory, which may let it run temporarily.
This code most often appears right after a control-board replacement, when the installer forgets to transfer the original model plug or fits the wrong one, or when a setup switch is bumped during service. Because getting staging and blower behavior right depends on these settings, a technician should verify the plug and switches against the wiring diagram.
What You'll Notice
- The code appears immediately after a control-board replacement or recent service
- The furnace may run on default settings, run incorrectly, or refuse to run
- The status LED flashes code 25 (two short flashes, five long flashes), or only 4 flashes when defaulting to stored settings
- Two-stage behavior or blower speeds may seem wrong for the model
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 → |
How This Is Diagnosed
A technician confirms the correct model plug is present and fully seated on PL4, matching the specific 355MAV model, and checks setup switches SW1-1 and SW1-6 against the furnace wiring diagram. If the code flashes only 4 times on power-up, that tells the technician the board is running on model settings stored in memory rather than the plug.
Since the fix is verifying and correcting the board's identification hardware and DIP settings — precise, model-specific configuration — it is handled by a qualified technician rather than the homeowner.
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:
- The furnace shows code 25 and the model plug or setup switches need verifying
- The code appeared after a control-board replacement or service visit
- Staging or blower behavior seems incorrect for your model
- You are unsure which model plug or DIP-switch settings are correct for the furnace
Frequently Asked Questions
Why did my Bryant 355MAV show code 25 after a new control board?
The most common reason is that the original model plug (PL4) was not transferred to the new board, or the wrong plug was fitted. The board then cannot identify the model correctly. A technician verifies the plug and setup switches.
Is code 25 dangerous?
It is a configuration error rather than a gas or safety fault, but it can make the furnace stage or run incorrectly. It should be corrected so the two-stage and variable-speed operation match the model as designed.
Sources
✓ Verified against manufacturer service manual — March 2026