Error Code PJ

If your Daikin VRV system is showing error code PJ, the system has detected that its configuration does not match the hardware installed.

There is something distinctive about this code: it is usually the result of a previous repair, not of anything wearing out.

What this means for your building

PJ indicates a field setting abnormality after the outdoor unit main control board was replaced, or an invalid combination of control boards.

VRV systems are configured through field settings — values that tell the control board what equipment it is managing: capacity, connected units, system configuration. Those settings live on the board.

Replace the board and the settings have to be transferred to the new one. If that step is skipped, the new board does not know what it is controlling.

The other case is a board combination the system does not consider valid — the wrong part fitted, or a pairing that is not supported for that equipment.

Why this is usually somebody’s previous repair

This is the most useful context on this page, particularly if you inherited a system or changed contractors.

PJ does not appear because a component aged out. It appears because a board was changed and the commissioning was incomplete. That means:

• If PJ appeared shortly after service work, that work is where to look
• If you have taken over a building and see PJ, it may have been there since a repair years ago
• Systems that have had multiple contractors are more likely to carry configuration faults

We see this most often in buildings where the original installing contractor is gone and subsequent repairs were done by whoever was available.

How urgent is it?

Less urgent than the protection codes, but genuinely worth resolving.

Nothing is being physically damaged. There is no refrigerant escaping and no compressor at immediate risk.

The problem is that the system is running on a configuration it does not recognise as valid. Capacity settings may not match the installed equipment, and protective functions calibrated to the real hardware may not behave as designed. You have a system whose safety and capacity behaviour cannot be fully relied on.

What it typically costs

Potentially high, and the range is unusually wide because two very different scenarios produce the same code.

If the settings simply need correcting, this is a technician visit. Someone who knows the platform enters the correct field settings and the code clears. Relatively inexpensive.

If the board combination is genuinely invalid, hardware has to change — and a main outdoor control board or inverter module is a substantial part.

Diagnosis determines which situation you are in, and it is worth doing before anyone orders parts.

What causes it

• Control board replaced without transferring field settings — by far the most common
• Field settings entered incorrectly during commissioning or after a repair
• Invalid board combination — an incorrect or unsupported part fitted
• Capacity setting mismatch against the equipment actually installed
• Incomplete commissioning on a system that was never correctly set up from new

What happens if you leave it

The system continues operating outside its intended configuration.

That may look fine day to day. The risk is that capacity and protection are calibrated to a description of the system that is not accurate. A protective function set for different equipment may not intervene when it should.

There is also a practical cost. Every future service visit starts from a system whose configuration cannot be trusted, which adds time to diagnosing anything else.

What we check

1. Read the current field settings and compare them against the equipment actually installed.
2. Identify what changed — service history is the fastest route to the cause.
3. Verify board part numbers and confirm the combination is valid for the equipment.
4. Check capacity settings against the connected indoor units.
5. Correct and verify the configuration, then confirm the system accepts it.
6. Document the settings, so the next board replacement does not recreate this.

That last step is one people skip, and it is why this fault recurs in some buildings.

What you can tell us before we arrive

• Has a control board been replaced? Even years ago. This is the single most useful thing you can tell us.
• Who did the last work on this system? Not to assign blame — it tells us what may have been done.
• Has this code been present a long time? Some buildings have carried PJ for years without realising.
• Do you have any commissioning documentation? Rare, but it saves considerable time when it exists.

Related codes

• U4 — Communication error. Can also follow incomplete work on the control system.
• L5 / L8 — Compressor faults. Worth knowing that incorrect capacity settings can contribute to equipment being run inappropriately.

Get the configuration corrected

We are certified on Daikin, Mitsubishi and LG VRF platforms, and we service systems we did not install — which includes sorting out configuration left behind by previous contractors.

Next business day service for commercial VRF.