Daikin VRV IV RXTQ-TA / RXTQ-TB error code J5
Suction pipe thermistor abnormality, R3T and R5T
Which models this applies to. Outdoor unit
Quick answer
On Daikin VRV IV RXTQ-TA / RXTQ-TB, J5 is a fault. It means suction pipe thermistor abnormality, r3t and r5t. A first thing to check: A failed R3T or R5T thermistor.
- Applies to
- Daikin VRV IV RXTQ-TA / RXTQ-TB
- Daikin VRV IV RXTQ heat pump codes · Heat Pump
- Type of code
- Fault
- Urgency: Book a technician
- First safe check
- Check both R3T and R5T, since the code covers two sensors and either one can cause it.
What J5 means on this model
Two sensors, R3T and R5T, on the suction line have reported a fault. Superheat cannot be calculated without them, so both need checking rather than only the first one found. Note this is the outdoor suction line sensor, not the C9 indoor return air sensor.
Symptoms you will notice
- Outdoor unit shows J5 and the system stops
- The system will not start or will not hold capacity
- The system runs but does not reach setpoint
- The fault followed work on the outdoor unit
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 failed R3T or R5T thermistor
- A loose or broken wire at one of the sensors
- A disturbed connector
- A clip that has come loose so the sensor is not reading the suction line
- A thermistor whose resistance is out of range
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.
- Check both R3T and R5T, since the code covers two sensors and either one can cause it.
- Confirm the sensors are still clipped to the suction line and that the wires are not chafed.
- Check the connectors at both sensors.
Do not do these
- ×Do not check only the first sensor you find. The manual names two, and replacing the wrong one leaves the code in place.
- ×Do not work on the connectors with the power switch on.
When to call a technician
Worth scheduling, and worth your own checks first
You can usually keep living with this for a short while, but it will not fix itself. Do the safe checks below first, because a tripped switch or a blocked airflow is a five-minute fix that would otherwise cost you a service call.
- 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
Suction thermistor $30 to $90 each.
Labor
One to two hours to test and replace.
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.