Daikin VRV IV RXTQ-TA / RXTQ-TB error code UE
Transmission error between the centralized controller and an indoor unit
Which models this applies to. System
Quick answer
On Daikin VRV IV RXTQ-TA / RXTQ-TB, UE is a fault. It means transmission error between the centralized controller and an indoor unit. A first thing to check: A communication fault between the centralized controller and the indoor unit.
- Applies to
- Daikin VRV IV RXTQ-TA / RXTQ-TB
- Daikin VRV IV RXTQ heat pump codes · Heat Pump
- Type of code
- Fault
- Urgency: Needs attention soon
- First safe check
- Identify which indoor unit or zone is offline, since that narrows the fault to a section of the bus.
What UE means on this model
A centralized controller cannot communicate with an indoor unit it is supposed to control. Unlike U5, this runs through the system bus rather than a short controller cable, so the break can be anywhere between the controller and that unit.
Symptoms you will notice
- System shows UE and an indoor unit or zone is offline
- A zone does not respond to the centralized controller
- The fault appears when a new zone is commissioned
Common causes
The code tells you what the control detected, not which part failed. These are the causes we see most often, roughly in order of likelihood:
- A communication fault between the centralized controller and the indoor unit
- An addressing mismatch between the controller and the indoor unit
- A failed indoor unit PCB
- A loose or disconnected bus connection
- A centralized controller that has exceeded the permitted number of units on its bus
What you can safely check
These are homeowner-level checks. None of them need you to open a live electrical compartment or work on gas.
- Identify which indoor unit or zone is offline, since that narrows the fault to a section of the bus.
- Check the addressing between the centralized controller and the offline unit.
- Check the bus connections between the controller and the affected part of the system.
Do not do these
- ×Do not add indoor units to a centralized controller bus beyond its limit, because the controller will lose contact with units further along the run.
- ×Do not work on the bus wiring with the power switch on.
When to call a technician
Book a technician, do not keep resetting it
This fault will not clear on its own. Every power cycle gives the control one more failed attempt, and repeated attempts are what turn a cheap part replacement into a seized or contaminated system.
- The refrigerant circuit is sealed and legally requires licensed handling. Opening it without certification releases refrigerant and can put the whole system in violation of regulation, so a low-pressure or high-pressure fault on this equipment is a call-out, not a weekend job.
- If the appliance has stopped mid-cycle, is making a noise you have not heard before, or smells burnt, stop reading here and call. Those are symptoms of something the fault code does not describe well enough.
A technician job.
What it costs to fix
Parts
Indoor unit PCB $200 to $450. Centralized controller $400 to $1,200.
Labor
Two to four hours to trace and correct the fault.
DIY or technician
A technician job.
Typical US part and labor ranges, 2026. They vary by region, model and contractor, so treat them as a planning figure, not a quote.
Scope of this code
- Code table
- Daikin VRV IV RXTQ heat pump codes
- Models in scope
- Daikin VRV IV RXTQ-TA / RXTQ-TB
- Checked
- Confirm on your own unit
- Find the model number on the data plate, then check this code in the service manual for that model. Manufacturers revise code tables between model years, and a revised board can renumber a fault.