If your Daikin VRV system is showing error code E4, low-side pressure fell below its safe threshold and the system stopped.
The instinct on any low pressure fault is to assume a refrigerant leak. On commercial VRV that instinct is frequently wrong, and acting on it is expensive.
What this means for your building
The low pressure sensor watches the suction side of the refrigerant circuit. When pressure falls too far, the system stops rather than run the compressor in conditions that damage it.
Pressure falls for three broad reasons, and they cost very different amounts:
- There is less refrigerant than there should be — a leak
- Refrigerant cannot flow properly — a failed expansion valve or a restriction
- The sensor is reading incorrectly — the cheapest outcome
Why this is not automatically a leak
This is the most useful thing on this page.
A VRV system contains many electronic expansion valves, metering refrigerant flow to each indoor unit. When one fails — sticking, losing its drive signal, or failing electrically — flow downstream drops and low-side pressure falls with it.
On a gauge, that looks very similar to a refrigerant shortage.
The difference matters enormously:
- If it is a leak, you need leak detection, repair, evacuation and recharge
- If it is a valve, you need a component replaced and the charge is fine
Adding refrigerant to a system with a restriction does not fix it. Worse, it can overcharge the system, creating a high pressure problem on top of the original fault. You have then paid for refrigerant that was never needed and introduced a second issue.
How urgent is it?
Urgent, for whichever reason applies.
If it is a leak, refrigerant is escaping now and the volume lost drives the recharge cost.
If it is a restriction, the compressor is running with inadequate refrigerant returning to it — which means poor oil return and elevated operating temperature.
Either way the component at risk is the compressor, which is the most expensive part of the system.
What it typically costs
Medium to high, and the range is wide.
A faulty low pressure sensor is a modest repair. An expansion valve replacement is a moderate component job, though access on a large system can add to it. A refrigerant leak on commercial VRV is the expensive end, because of the charge volume and the work required to locate, repair, test, evacuate and recharge.
The good news: diagnosis genuinely saves money here. Establishing that you have a valve problem rather than a leak avoids a substantial and unnecessary refrigerant bill.
What causes it
- Failed or stuck electronic expansion valve — common on VRV given how many there are
- Refrigerant leak — the scenario most people assume first
- Blocked filter or drier creating a restriction
- Restriction in the pipework from damage, kinking, or debris
- Faulty low pressure sensor reporting a drop that is not real
- Undercharge from previous work where the system was never correctly filled
What happens if you leave it
The compressor absorbs the consequences.
Refrigerant carries oil around the circuit and helps cool the compressor. Whether the shortfall comes from a leak or a restriction, the compressor is running hot and under-lubricated.
If the cause is a leak, that also keeps growing, and so does the eventual recharge cost.
What we check
- Verify the sensor reading is genuine before assuming anything about charge.
- Measure system pressures across the circuit to see where the drop occurs.
- Test expansion valve operation — this is the differentiator from a simple leak, and it comes early rather than late.
- Assess refrigerant charge against system design.
- Leak detection if the charge is genuinely low.
- Inspect filters and driers for restriction.
- Review service history — prior top-ups usually mean an unrepaired leak.
What you can tell us before we arrive
- Has refrigerant been added before? Prior top-ups point strongly toward a leak.
- Is one zone affected or many? A single zone behaving differently can point at a specific expansion valve.
- When did capacity start dropping? Gradual loss often precedes the code.
- Has any work been done on the pipework? Recent disturbance is relevant.
Related codes
- U0 — Refrigerant shortage. Related but distinct; both can appear when charge is genuinely low.
- E3 — High pressure. The opposite condition, and what you can create by overcharging in response to E4.
- L5 / L8 — Compressor faults. Where sustained low-side problems eventually lead.
Get it diagnosed before anyone adds refrigerant
We are certified on Daikin, Mitsubishi and LG VRF platforms, and we service systems we did not install.
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Related codes
Error U0 means refrigerant shortage. On a large commercial VRV system this is one of the most expensive faults there is, and it gets worse the longer it runs.
Error E3 means the high pressure switch activated. The shutdown protected your compressor — but the condition that caused it damages compressors if left alone.
Error L5 is compressor instantaneous overcurrent — a sudden current spike that most often means a shorted or grounded compressor motor. Do not restart it.
Frequently asked questions
What does error code E4 mean on a Daikin VRV system?
The low pressure sensor detected pressure below its safe threshold and the system stopped. Something is preventing refrigerant reaching the low side at the expected pressure, which on commercial VRV is often a flow restriction rather than simply a shortage of refrigerant.
Is E4 the same as a refrigerant leak?
Not necessarily, and this is where E4 differs from U0. A leak produces low pressure, but so does a failed electronic expansion valve or a severe restriction in the pipework. Diagnosis has to distinguish them, because the repairs are entirely different.
What is an electronic expansion valve and why does it fail?
It meters refrigerant flow into the evaporator, and a VRV system has many of them. They can stick, fail electrically, or lose their drive signal. When one stops metering correctly the pressure downstream drops, which is exactly what this code reports.
Can a blocked filter cause an E4 error?
Yes. A restriction anywhere in the liquid line, including a blocked filter or drier, reduces flow and drops low-side pressure. It presents very similarly to a refrigerant shortage on gauges, which is why adding refrigerant is the wrong first response.
Why should I not just add refrigerant to clear an E4?
Because if the cause is a restriction rather than a shortage, adding refrigerant does not fix it and can overcharge the system. That creates a high pressure problem on top of the original fault, and you have paid for refrigerant that was never needed.
How much does an E4 error cost to fix?
Medium to high, with real range. A faulty sensor is modest. An expansion valve replacement is a moderate component repair. If the underlying cause turns out to be a refrigerant leak on a large VRV system, the cost rises considerably.