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Error code reference

LG Hvac Error Code E202

System failure by communication error

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System failure by communication error — MASTER to SLAVE communication failure continues for 2 minutes after tracking is completed.

First step from the service manual

Press RESET KEY K3 on MASTER PCB to check number of SLAVEs responding to tracking.

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

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What E202 means on a LG hvac

The LG E202 error code indicates a communication failure between the MASTER PCB and one or more SLAVE units in a multi-split or VRF system. Specifically, this fault is triggered when the MASTER-to-SLAVE communication link fails to maintain a stable connection for a continuous period of 2 minutes after the system has completed its tracking sequence. Tracking is the initialization process in which the MASTER controller identifies and registers all connected SLAVE units on the network. When communication cannot be sustained past that point, the system logs E202 to alert the technician that the indoor unit network is partially or fully unresponsive.

The communication network in these systems typically runs over a dedicated signal wiring bus connecting the MASTER PCB to each SLAVE unit PCB. Faults can originate from wiring issues such as open circuits, short circuits, incorrect polarity, or excessive resistance on the communication lines. Faulty or failed SLAVE PCBs that stop responding after initial tracking can also produce this fault. Additionally, electrical noise from improperly grounded components or nearby high-voltage wiring can corrupt communication signals, causing intermittent or sustained failures.

The first diagnostic step is to press the RESET KEY K3 on the MASTER PCB to initiate a fresh tracking sequence and observe how many SLAVE units respond. If fewer SLAVEs respond than are physically installed, the missing units should be inspected for wiring integrity, power supply issues at the indoor unit, and PCB functionality. Comparing the number of registered SLAVEs before and after the reset helps isolate whether the problem is isolated to one unit or systemic across the entire installation.

Source: manufacturer service documentation.

Common causes of E202

  1. 01

    Damaged or loose communication wiring

    Wiring / connection

    Open circuits, loose terminal connections, or damaged insulation on the signal wiring bus between the MASTER and SLAVE units are the most frequent cause. Inspect all communication wire terminals at each unit for tightness, corrosion, and continuity.

  2. 02

    Incorrect wiring polarity on communication bus

    Wiring / connection

    Reversed polarity on the communication signal lines will prevent the MASTER PCB from receiving responses from SLAVE units after tracking. Verify that wiring polarity matches the wiring diagram at every connection point.

  3. 03

    Failed SLAVE unit PCB

    Part replacement

    A defective indoor unit PCB may respond during initial tracking but drop off the communication network within the 2-minute window. After pressing RESET KEY K3, compare the number of responding SLAVEs to the number installed to identify which unit is failing.

  4. 04

    Loss of power to one or more SLAVE units

    Wiring / connection

    If an indoor unit loses its power supply, the SLAVE PCB cannot maintain communication after tracking is complete. Check for tripped breakers, blown fuses, or wiring faults at the power input of each indoor unit.

  5. 05

    Electrical noise or grounding issues

    Wiring / connection

    Improper grounding or communication wiring routed too close to high-voltage power cables can introduce noise that corrupts the signal bus. Verify all units are properly grounded and that communication wiring is separated from line-voltage conductors.

See the test procedure for each cause

Frequently asked questions about E202

What does E202 mean on a LG hvac?
The E202 code on an LG multi-zone or VRF system indicates a sustained MASTER-to-SLAVE communication failure. After the system completes its tracking sequence, the MASTER PCB cannot maintain contact with one or more SLAVE indoor unit PCBs for 2 consecutive minutes. This causes the system to halt operation and log the fault code.
Can I reset an E202 error myself?
You can initiate a diagnostic reset by pressing the RESET KEY K3 on the MASTER PCB, which triggers a new tracking sequence and shows how many SLAVE units are responding. However, this reset alone will not clear the fault if the underlying communication problem persists. If any indoor units fail to respond after the reset, a technician will need to inspect wiring and PCBs at those units.
Is it safe to continue using my system with an E202 error?
The system will typically stop operating normally when E202 is active, so continued use is not usually possible without clearing the fault. It is not advisable to bypass or ignore the error, as unresolved communication faults can mask underlying electrical or hardware issues that may worsen over time. Contact a qualified HVAC technician for diagnosis.
How much does it cost to repair an E202 error on an LG system?
Repair costs vary depending on the root cause. If the fix involves re-terminating or replacing communication wiring, costs are generally lower, typically in the range of $100 to $300 for labor. If one or more SLAVE PCBs need to be replaced, parts and labor combined can range from $300 to $800 or more per unit depending on the model and local rates.
Will resetting the system permanently clear the E202 code?
Pressing RESET KEY K3 on the MASTER PCB clears the fault temporarily and restarts the tracking process, but the E202 code will return if the communication issue is not resolved. A permanent fix requires identifying and correcting the specific cause, such as repairing wiring, restoring power to affected indoor units, or replacing a faulty SLAVE PCB.

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