Honeywell UDC2500 Digital Controller
Honeywell UDC2500 Digital Controller code 05, 06: Slave Device Busy
The controller cannot communicate because the addressed slave device rejected a message due to being busy.
- Code
- 05, 06
- Name
- Slave Device Busy
- Controller
- Honeywell UDC2500 Digital Controller
- Type
- Communication
- What it does
- Warning: the equipment keeps running and flags a problem
- Risk
- GREEN In your wheelhouse
- Reset
- Clears on its own when the condition goes away
- Source
- The manufacturer's manual (subscribers see which manual and page)
Updated November 4, 2026
How to fix it
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- What to do next, in plain words
- What the manual says to do, and the page it is on
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Questions about this code
What does Honeywell UDC2500 Digital Controller code 05, 06 mean?
The controller cannot communicate because the addressed slave device rejected a message due to being busy.
Is Honeywell UDC2500 Digital Controller code 05, 06 dangerous?
It is graded green: in a working tech's wheelhouse with standard tools and low risk.
How do I fix Honeywell UDC2500 Digital Controller code 05, 06?
The manual's fix and the step by step check for this code are in WERCS Diagnose, plans from $49 a month. For help right now, WERCS answers 24/7 at (877) 489-3727.
Other Honeywell UDC2500 Digital Controller codes
01 · Illegal Function02 · Illegal Data Address03 · Illegal Data Value04 · Slave Device Failure07 · NAK, Negative Acknowledge09 · Buffer OverflowLOCK · LOCKPV LIM · PV LIMEE FAIL · EE FAIL
All 10 Honeywell UDC2500 Digital Controller codes · Every fault code