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Error code reference

LG Microwave Error Code E-b2

Cooling fan motor PCB temperature over 75°C error.

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Cooling fan motor PCB temperature over 75°C error.

First step from the service manual

Check if cooling motor is rotating; check motor drive part.

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

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What E-b2 means on a LG microwave

The E-b2 error code on an LG microwave indicates that the PCB (printed circuit board) temperature has exceeded 75°C, triggered by the cooling fan motor system failing to maintain adequate airflow across the control board. The microwave's cooling fan is responsible for drawing heat away from the PCB and other internal components during operation. When this fan slows down, seizes, or stops rotating entirely, heat builds up rapidly on the board. A thermal sensor monitors PCB temperature continuously, and once it crosses the 75°C threshold, the unit halts operation and displays E-b2 to prevent component damage.

The most direct diagnostic step is to confirm whether the cooling fan motor is actually spinning during operation. If the motor is not rotating, the fault could lie in the motor itself, the motor drive circuitry on the PCB, or the wiring connecting these components. Blocked ventilation ports can also reduce airflow enough to cause overheating even when the fan is spinning at full speed. Debris, grease buildup, or a physical obstruction in the fan blade path are common contributors in kitchen environments.

Because this error involves both a mechanical component (the fan motor) and its associated drive circuitry, diagnosis requires checking both sides of the system. A motor that tests within normal resistance specifications but fails to spin may point to a failed motor driver stage on the control board. Conversely, a motor with an open winding or a seized bearing will cause the driver to work harder and may also damage the drive circuitry over time.

Source: manufacturer service documentation.

Common causes of E-b2

  1. 01

    Cooling fan motor failure

    Part replacement

    The fan motor may have seized bearings or an open winding, preventing it from spinning. You can often confirm this by listening for fan noise during operation or manually checking if the fan blade turns freely when the unit is unplugged.

  2. 02

    Blocked or obstructed fan

    Wiring / connection

    Grease buildup, debris, or a foreign object lodged in the fan blade assembly can stop rotation or severely restrict airflow. Inspect the fan blade visually and clean any accumulation of grease or debris from the blades and surrounding housing.

  3. 03

    Failed motor drive circuitry on the PCB

    Part replacement

    If the fan motor itself checks out mechanically and electrically, the driver circuit on the control board that powers the motor may have failed. This requires board-level inspection or full PCB replacement.

  4. 04

    Wiring harness fault between PCB and fan motor

    Wiring / connection

    A broken, corroded, or disconnected wire between the control board and the fan motor will prevent the motor from receiving power. Inspect the connector and wire harness for continuity and secure connections.

  5. 05

    Blocked ventilation ports on the microwave cabinet

    Wiring / connection

    If the external air intake or exhaust vents on the microwave are blocked by the surrounding cabinetry or wall, airflow through the unit is restricted and PCB temperature can rise even with a functioning fan. Ensure the unit has adequate clearance on all vented sides.

See the test procedure for each cause

Frequently asked questions about E-b2

What does E-b2 mean on a LG microwave?
E-b2 on an LG microwave means the control board (PCB) temperature has exceeded 75°C, which is the safety threshold for this component. The microwave detected that its cooling fan motor is not keeping the board cool enough. The unit shuts down automatically to prevent damage to the electronics. The root cause is typically a non-rotating or underperforming cooling fan motor or a problem with the motor drive circuit.
Can I fix the E-b2 error myself?
Some causes of E-b2 are DIY-friendly, such as clearing a blocked fan blade or checking that the microwave's ventilation openings are not obstructed. However, replacing the cooling fan motor or diagnosing a fault in the motor drive circuitry on the PCB requires disassembly of the microwave and should only be performed by someone comfortable working around high-voltage appliances. Microwaves retain dangerous voltage in their capacitors even when unplugged, so internal repairs carry serious risk if performed without proper precautions.
Is it safe to use my LG microwave while it shows E-b2?
No, you should not attempt to operate the microwave while E-b2 is active. The error indicates the PCB is already overheating, and continued use without a functioning cooling fan can permanently damage the control board and other internal components. The microwave's automatic shutdown is a protective measure, and bypassing or ignoring it can lead to more extensive and costly repairs.
Will resetting my LG microwave clear the E-b2 error?
Unplugging the microwave for a minute and restoring power may temporarily clear the error if the board has cooled down, but the code will return once the unit is used again if the underlying problem is not fixed. A reset does not repair a failed fan motor or faulty drive circuitry. Clearing the code without addressing the root cause risks additional damage to the PCB.
How much does it cost to repair an LG microwave E-b2 error?
Repair costs vary depending on the root cause. A replacement cooling fan motor part typically costs in the range of $15 to $50, while a full control board replacement can range from $80 to $200 or more depending on the model. If you hire a technician, labor charges will add to these figures and total repair costs could approach or exceed the value of an older unit. Getting a diagnostic estimate before committing to parts replacement is advisable.

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