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Error code reference

LG Refrigerator Error Code I/M-SENSOR

Ice maker sensor error

LG codesLG refrigerator codes

Ice maker sensor error: electric wire cut, short-circuit, contact failure, or sensor housing missing; displayed when sensor temperature is not lower than 122°F nor higher than -58°F.

First step from the service manual

Check the voltage between Main PCB CN 90 No. 3 ↔ 4 to see if it is between 4.5V and 1.0V.

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

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What I/M-SENSOR means on a LG refrigerator

The I/M-SENSOR error code on an LG refrigerator indicates a fault within the ice maker temperature sensor circuit. This sensor monitors the thermal conditions inside the ice maker compartment and reports back to the main PCB. The error triggers when the sensor reads a temperature outside the valid operating range: not lower than -58°F and not higher than 122°F. Any reading outside this window is treated as a circuit anomaly rather than a real temperature, causing the control board to flag the fault and suspend normal ice maker operation.

The four primary causes of this error are an open wire (cut or broken), a short circuit in the sensor wiring harness, a contact failure at a connector, or a missing sensor housing. Each of these conditions distorts or eliminates the signal the main PCB receives from the sensor. The first diagnostic step is to check the voltage between Main PCB connector CN 90, pins 3 and 4. A healthy sensor circuit will read between 1.0V and 4.5V at this test point. A reading outside that range, or no voltage at all, confirms an electrical fault in the sensor loop and directs the technician toward the wiring, connector, or sensor itself.

Because the ice maker sensor is part of a dedicated circuit tied to the main control board, a fault here will not affect the refrigerator or freezer compartment cooling. However, ice production will halt until the fault is resolved. Diagnosis should follow a logical path: inspect the wiring harness and connectors for visible damage or corrosion first, then test sensor resistance to determine whether the component itself has failed, and finally verify the main PCB output if the sensor and wiring both test within specification.

Source: manufacturer service documentation.

Common causes of I/M-SENSOR

  1. 01

    Connector contact failure at CN 90

    Wiring / connection

    Loose, corroded, or partially seated connector pins at Main PCB CN 90 pins 3 and 4 are a frequent cause of this error. Check the connector for corrosion, bent pins, or incomplete seating and test voltage across those pins to confirm.

  2. 02

    Broken or cut sensor wiring harness

    Part replacement

    Physical damage to the wire running from the main PCB to the ice maker sensor can interrupt the circuit entirely. Inspect the harness along its full routing path for cuts, pinches, or breaks, particularly at points where the wire bends or passes through a door hinge.

  3. 03

    Failed ice maker temperature sensor

    Part replacement

    The sensor itself can fail internally due to age or moisture exposure, causing it to read outside the valid temperature range. If wiring and connectors check out, the sensor should be tested for proper resistance and replaced if it is out of specification.

  4. 04

    Short circuit in the sensor circuit

    Part replacement

    A short in the sensor wiring or at the sensor terminals can pull the voltage reading outside the 1.0V to 4.5V window. This often results from chafed insulation allowing two wires to contact each other or a grounded wire touching the appliance chassis.

  5. 05

    Missing or improperly seated sensor housing

    Wiring / connection

    If the sensor housing is absent or not fully secured in its mounting location, the sensor may not make proper thermal or electrical contact. Visually confirm the sensor is present, correctly installed, and fully seated in its housing.

See the test procedure for each cause

Frequently asked questions about I/M-SENSOR

What does I/M-SENSOR mean on a LG refrigerator?
The I/M-SENSOR code means the refrigerator has detected a fault in the ice maker temperature sensor circuit. The error appears when the sensor reports a temperature outside the range of -58°F to 122°F, which the control board interprets as a wiring, connection, or sensor failure rather than a real temperature reading. Common causes include a broken wire, a short circuit, a loose connector, or a missing sensor housing. Ice production will stop while this code is active.
Can I fix the I/M-SENSOR error myself?
Some causes of this error are DIY-friendly. Start by inspecting the wiring harness connected to the ice maker sensor and checking the connector at Main PCB CN 90 pins 3 and 4 for corrosion or loose fit. If you have a multimeter, you can test for voltage between those pins: a reading between 1.0V and 4.5V indicates the circuit is intact. Replacing a sensor or wiring harness is within reach for experienced DIYers, but working near the main PCB carries some risk, and a certified technician should be consulted if you are unsure.
Is it safe to use my LG refrigerator while the I/M-SENSOR code is showing?
Yes, the refrigerator and freezer compartments should continue to cool normally while this code is active because the ice maker sensor circuit is separate from the main cooling system. The primary impact is that ice production will be suspended. You can continue using the appliance for food storage, but the issue should be diagnosed and repaired to restore ice maker function.
Will resetting my LG refrigerator clear the I/M-SENSOR error?
A power reset may temporarily clear the error code from the display, but if the underlying fault in the sensor circuit is still present, the code will return once the refrigerator resumes normal operation and re-checks the sensor. A reset is useful for confirming whether the fault is intermittent, but it is not a repair. The wiring, connectors, and sensor need to be inspected and tested to resolve the error permanently.
How much does it cost to repair the I/M-SENSOR error on an LG refrigerator?
Repair costs vary depending on the root cause. If the fix is simply reseating a connector, there may be no parts cost, though a service call fee typically runs between $75 and $150. Replacing the ice maker temperature sensor usually costs between $20 and $60 for the part, plus labor. If the wiring harness needs replacement, total costs including labor can range from $100 to $250 or more. Main PCB replacement, if needed, is the most expensive outcome and can run from $200 to $400 or higher.

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