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Error code reference

LG Hvac Error Code E606

COM1/COM2 cross installation error

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COM1/COM2 cross installation error — wired remote control communication lines F1/F2 and F3/F4 are cross-connected.

First step from the service manual

Check terminal block of wired remote control connection; verify communication line is connected to COM2 (F3, F4).

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What E606 means on a LG hvac

The E606 error code on LG HVAC systems indicates a COM1/COM2 cross installation error. This fault occurs when the wired remote control communication lines are incorrectly wired at the terminal block. Specifically, the F1/F2 lines (which belong to COM1) and the F3/F4 lines (which belong to COM2) have been swapped or cross-connected during installation. The system detects this mismatch during communication handshaking between the indoor unit and the wired remote controller, triggering the fault code to prevent improper operation.

This is purely an installation wiring error rather than a component failure. The indoor unit expects the wired remote controller to communicate over the COM2 port, using terminals F3 and F4. When the wiring is reversed or crossed, the communication protocol breaks down and the unit cannot establish a valid connection with the remote controller. The error is most commonly introduced during initial installation, after a controller replacement, or following any rewiring work at the terminal block. Verifying that the communication line from the wired remote control is properly landed on the COM2 terminals (F3 and F4) is the first and most critical diagnostic step.

Source: manufacturer service documentation.

Common causes of E606

  1. 01

    Wired remote control lines connected to COM1 instead of COM2

    Wiring / connection

    The most frequent cause is landing the remote controller wires on the F1/F2 terminals (COM1) when they should be on F3/F4 (COM2). Inspect the terminal block and confirm the communication line is seated at F3 and F4.

  2. 02

    F1/F2 and F3/F4 pairs swapped at the terminal block

    Wiring / connection

    During installation or rewiring, the two pairs of communication lines may be fully transposed, connecting F3/F4 wiring to the F1/F2 terminals and vice versa. Visual inspection of each wire's terminal position against the wiring diagram will reveal this.

  3. 03

    Incorrect wiring after wired remote controller replacement

    Wiring / connection

    When a wired remote controller is replaced, technicians may reference the old unit's wiring without verifying terminal assignments on the new controller, resulting in a cross-connection. Always confirm COM2 (F3, F4) assignment after any controller swap.

  4. 04

    Miswiring at the remote controller end of the communication cable

    Wiring / connection

    The cross-connection may occur at the remote controller's terminal block rather than at the indoor unit. Both ends of the F1/F2 and F3/F4 wiring should be inspected to locate the point of error.

  5. 05

    Damaged or incorrectly labeled communication cable

    Wiring / connection

    A cable that was previously mislabeled or had conductors re-terminated incorrectly can introduce a cross-connection that is not obvious visually. Continuity testing of each conductor from end to end can confirm correct pairing.

See the test procedure for each cause

Frequently asked questions about E606

What does E606 mean on a LG hvac?
E606 indicates a COM1/COM2 cross installation error on your LG HVAC system. It means the communication wires for the wired remote controller are connected to the wrong terminals, specifically that the F1/F2 and F3/F4 lines have been cross-connected. The system flags this fault because it cannot establish proper communication between the indoor unit and the remote controller with the wiring in that state.
How do I fix the E606 error on my LG HVAC?
Start by powering down the unit and locating the terminal block where the wired remote controller connects to the indoor unit. Verify that the communication cable is connected to the COM2 port, using terminals F3 and F4, not F1 and F2. If the wires are on the wrong terminals, move them to the correct positions, restore power, and check whether the error clears. If you are unsure about identifying the correct terminals, consult a qualified HVAC technician.
Is the E606 error dangerous or a safety risk?
The E606 error itself is not a safety hazard. It is a wiring configuration fault that prevents proper communication between the indoor unit and the wired remote controller. The system flags it to avoid operating under an unintended configuration. No refrigerant, electrical overload, or fire risk is associated with this specific fault code.
Will resetting the unit clear the E606 error on a LG HVAC?
No, simply resetting the unit will not clear the E606 error. Because the fault is caused by a physical wiring error at the terminal block, the error will return immediately after a reset unless the cross-connected communication lines are corrected. The wiring must be properly reconnected to COM2 (F3 and F4) before the error will go away.
How much does it cost to fix an E606 error on a LG HVAC?
Since E606 is a wiring error rather than a parts failure, the cost is typically limited to a service call and labor charge, generally in the range of $75 to $200 depending on your location and the technician's rates. No replacement parts are normally required unless an inspection reveals that the communication cable itself is damaged and needs to be replaced, which could add a modest materials cost on top of labor.

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