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Error code reference

Daewoo Microwave Error Code Er03

Humidity sensor error during auto reheating operation

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Humidity sensor error during auto reheating operation - sensor circuit voltage out of expected range.

First step from the service manual

Check humidity sensor connection to CN3, verify resistors R6-R10, and check voltage at points A (0.5V-3.5V), B (11.3VDC), C (4.4VDC), D (2.2VDC) after 1-2 minutes of auto reheating operation.

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

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What Er03 means on a Daewoo microwave

The Er03 code on a Daewoo microwave indicates a fault in the humidity sensor circuit during an auto reheating operation. The humidity sensor monitors moisture released from food as it heats, allowing the microwave to automatically determine when the food is sufficiently reheated. When the control board detects that the sensor circuit voltage has fallen outside its expected operating range, it triggers Er03 and halts the auto reheat function to prevent incorrect cooking results.

The sensor circuit relies on a network of resistors, specifically R6 through R10, to condition the signal before it reaches the control board. During normal operation, after 1 to 2 minutes of auto reheating, the voltage at test point A should read between 0.5V and 3.5VDC, point B should read 11.3VDC, point C should read 4.4VDC, and point D should read 2.2VDC. A reading outside any of these expected values pinpoints where in the circuit the fault originates. The sensor connects to the board via connector CN3, making that connection a primary inspection point.

Common causes include a loose or corroded CN3 connector, a failed humidity sensor, or degraded resistors in the R6 to R10 network. Because the sensor operates in a humid, high-heat environment, connector pins can oxidize over time and introduce resistance into the circuit, skewing voltage readings. Physical damage to the sensor element itself, or a partial short caused by food residue contamination inside the cavity near the sensor, can also shift the signal voltage out of the acceptable window.

Source: manufacturer service documentation.

Common causes of Er03

  1. 01

    Loose or corroded CN3 connector

    Wiring / connection

    The humidity sensor plugs into the control board at connector CN3. If the connector is loose, has bent pins, or shows oxidation or corrosion, the circuit voltage will read incorrectly. Inspect the connector visually and reseat it firmly to check if this resolves the fault.

  2. 02

    Failed or contaminated humidity sensor

    Part replacement

    The sensor element itself can fail due to age, heat exposure, or contamination from food splatter inside the cavity. A failed sensor will produce a voltage at test point A that is consistently out of the 0.5V to 3.5VDC range even after reconnecting all wiring.

  3. 03

    Degraded or open resistors R6 to R10

    Part replacement

    The resistor network R6 through R10 conditions the sensor signal before it reaches the control board. If any of these resistors have drifted in value, burned, or opened, the reference voltages at test points B, C, and D will be incorrect. Check each resistor for the correct resistance value and look for signs of heat damage.

  4. 04

    Wiring harness damage between sensor and board

    Wiring / connection

    The wiring running from the humidity sensor to CN3 can develop breaks, pinches, or chafing damage, particularly if it is routed near a heat source. A broken wire will remove the sensor signal entirely, causing the voltage at point A to read near zero or at its maximum.

  5. 05

    Faulty control board

    Part replacement

    If all wiring, connector, sensor, and resistor values check out correctly but the reference voltages at points B, C, and D are still wrong, the control board itself may have a defect affecting the sensor input circuit. This is the least common cause and should be diagnosed only after ruling out all other components.

See the test procedure for each cause

Frequently asked questions about Er03

What does Er03 mean on a Daewoo microwave?
Er03 indicates a humidity sensor circuit error that occurs during the auto reheating operation. The control board has detected that the voltage in the sensor circuit is outside the expected range. This fault prevents the auto reheat feature from functioning correctly. The sensor, its connector at CN3, and the associated resistors R6 through R10 are the primary areas to inspect.
Can I fix Er03 myself without calling a technician?
Some causes of Er03 are accessible to a knowledgeable DIYer. Reseating the CN3 connector and visually inspecting the wiring harness for damage are reasonable first steps that require no special tools. However, testing the specific voltages at points A through D and checking resistor values requires a multimeter and familiarity with circuit boards. If those checks point to a failed sensor or control board, a qualified technician should handle the repair due to the high-voltage components present inside a microwave.
Is it safe to keep using my microwave when Er03 appears?
When Er03 is active, the auto reheat function is disabled, meaning you should not rely on that feature to properly heat food. Manual cooking modes may still operate, but using the appliance with an unresolved sensor fault is not recommended for extended periods. You should have the sensor circuit inspected before continuing regular use.
Will resetting the microwave clear the Er03 code?
Unplugging the microwave and restoring power may temporarily clear the error display, but Er03 will return as soon as the auto reheat cycle is used again if the underlying fault in the humidity sensor circuit has not been corrected. A reset does not repair a failed sensor, damaged wiring, or defective resistors. Address the root cause to permanently resolve the code.
How much does it cost to repair a Daewoo microwave showing Er03?
Repair costs vary depending on which component has failed. Reseating a connector costs nothing beyond your time. Replacing the humidity sensor typically falls in the range of $20 to $60 for the part alone, plus labor if a technician is used. A control board replacement is the most expensive scenario, generally ranging from $80 to $150 or more for the part. Factor in that a technician diagnostic fee often runs $50 to $100, which may be applied toward the total repair cost.

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