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Error code reference

LG Microwave Error Code E-51

EEPROM open error

LG codesLG microwave codes

EEPROM open error - sense failure.

First step from the service manual

Replace EEPROM and restart; check if proper EEPROM (R4LCO40 or 24LCO4) has been installed.

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

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What E-51 means on a LG microwave

The E-51 error code on an LG microwave indicates an EEPROM open error, specifically categorized as a sense failure. The EEPROM (Electrically Erasable Programmable Read-Only Memory) is a small non-volatile memory chip that stores critical configuration data for the microwave, including calibration settings, operational parameters, and user preferences. When the control board cannot establish proper communication with the EEPROM or detects that the chip is unresponsive, it triggers the E-51 fault and halts normal operation.

This error is most commonly linked to an incorrect EEPROM chip being installed during a previous repair, or a chip that has failed outright. LG specifies compatible EEPROM chips for this application as the R4LCO40 or the 24LCO4. Installing an incompatible chip, even one that appears physically similar, will cause the control board to fail to read or write data correctly, resulting in the open error condition. A chip that has experienced data corruption or internal failure will produce the same result.

Diagnosis should begin by confirming which EEPROM is currently installed and verifying it matches one of the two specified part numbers. If the correct chip is already in place, the chip itself has likely failed and requires replacement. In some cases, the control board circuitry that interfaces with the EEPROM, including solder joints and traces, may also be responsible if the chip tests as the correct type but the error persists after replacement.

Source: manufacturer service documentation.

Common causes of E-51

  1. 01

    Incorrect EEPROM chip installed

    Part replacement

    A previous repair may have used an incompatible EEPROM chip. The only compatible chips are the R4LCO40 and the 24LCO4. Any other chip will cause the control board to report an open error.

  2. 02

    Failed EEPROM chip

    Part replacement

    The EEPROM chip can fail due to age, voltage spikes, or data corruption, leaving it unresponsive to the control board. If the correct chip type is already installed and the error persists, the chip has likely failed and must be replaced.

  3. 03

    Poor solder connection on EEPROM

    Wiring / connection

    A cold or cracked solder joint at the EEPROM pins can create an open circuit condition that mimics chip failure. Inspect the solder joints under magnification and reflow or re-solder as needed.

  4. 04

    Control board communication fault

    Part replacement

    If EEPROM replacement with the correct chip does not clear the error, the control board circuitry responsible for EEPROM communication may be damaged. This can include damaged traces or failed support components on the board.

See the test procedure for each cause

Frequently asked questions about E-51

What does E-51 mean on a LG microwave?
E-51 indicates an EEPROM open error, which means the microwave control board cannot communicate with its onboard memory chip. This chip stores operational settings and is required for normal function. The error is typically caused by a missing, incorrect, or failed EEPROM chip. The two compatible chip types for LG microwaves displaying this code are the R4LCO40 and the 24LCO4.
How do I fix the E-51 error on my LG microwave?
Start by checking which EEPROM chip is installed and confirming it is either the R4LCO40 or the 24LCO4. If the wrong chip is present, replace it with one of the correct types and restart the microwave. If the correct chip is already installed and the error continues, the chip has likely failed and should be replaced. Persistent errors after chip replacement may point to a control board issue.
Will resetting the microwave clear the E-51 error?
A basic power reset, such as unplugging the unit for a few minutes, will not clear the E-51 error if the underlying EEPROM problem remains. The error will return immediately on startup because the control board checks EEPROM communication during its initialization sequence. The fault can only be resolved by installing a functioning, correct EEPROM chip.
Is it safe to use my LG microwave when E-51 is displayed?
The microwave will not operate normally while displaying E-51, as the control board has halted function due to the memory fault. You should not attempt to force operation. The unit should remain unplugged until the EEPROM issue is diagnosed and corrected.
How much does it cost to repair an E-51 error on an LG microwave?
If only the EEPROM chip requires replacement, parts cost is generally low, typically in the range of a few dollars to around $20 depending on the source. If professional labor is involved, total repair costs can range from $75 to $200 or more depending on the service provider and whether any additional components such as the control board need replacement.

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