Daikin VRV IV RXTQ-TA / RXTQ-TB error code E4
Low pressure protection activation
Which models this applies to. Outdoor unit
Quick answer
On Daikin VRV IV RXTQ-TA / RXTQ-TB, E4 is a fault. It means low pressure protection activation. A first thing to check: A refrigerant leak.
- 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
- Note whether the system stops quickly after startup, which points at low pressure rather than high.
What E4 means on this model
The low side pressure has dropped far enough for the low pressure protection to operate and the outdoor unit has shut down. A refrigerant leak, a closed expansion valve and a failing compressor all present this way, and the system usually stops quickly rather than after a long run.
Symptoms you will notice
- Outdoor unit shows E4 and the system stops
- The system stops quickly rather than running for a long time
- The system stops on a cooling or heating demand with no other symptom
- The outdoor fan runs but the compressor does not
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 refrigerant leak
- A failed low pressure sensor
- A closed or restricted electronic expansion valve
- A failed compressor causing low suction pressure
- A suction line restriction
- An incorrectly installed or undersized expansion device
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.
- Note whether the system stops quickly after startup, which points at low pressure rather than high.
- Look for evidence of a leak around the outdoor unit joints and around the indoor unit, such as oil staining or a frost patch on the piping.
- Check that the outdoor fan is running normally, because a fan fault that reduces refrigerant flow can also pull pressure down.
Do not do these
- ×Do not add refrigerant to clear E4 without finding the leak. Any charge added to a leaking system is lost and the compressor is left exposed.
- ×Do not reset and retry repeatedly. Low pressure protection exists to stop air and oil being drawn into the compressor.
- ×Do not work on the refrigerant circuit without recovery equipment and the factory procedures.
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 licensed technician job. Looking for oil staining around the piping is reasonable for a homeowner.
What it costs to fix
Parts
Low pressure sensor $60 to $180. Replacement EEV $150 to $400 plus coil.
Labor
Two to four hours to find a leak, plus recovery and recharge.
DIY or technician
A licensed technician job. Looking for oil staining around the piping is reasonable for a homeowner.
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.