Error code · Microwave

Reading E21 on a Whirlpool Over-the-Range Microwave: Open Thermal Sensor Circuit

Medium · inspection needed

Code: E21
Appliance: Microwave
Brand: Whirlpool
Warranty: 30-day workmanship

What E21 means

E21 on Whirlpool over-the-range microwaves, such as models WMH31017HS, WMH32519HZ and WMH53521HZ, means the thermal sensor circuit reported an open condition to the control board. In plain words, the control sees a break in the loop that should carry the temperature reading. The thermal sensor, the appliance control board or the wiring between them may be responsible. You will see E21 in the display and the oven may not start or may stop mid-cycle.

Common causes of E21

Thermal sensor
Wiring or connector with a break
Appliance control board

✓ One safe check you can try

1. Turn off the microwave's circuit breaker and wait one minute. 2. Turn the breaker on. 3. Watch the display for one minute and confirm E21 does not return. 4. Try a short cycle to check that the oven runs. 5. If it returns, stop using the oven and let us test it.

! Why to stop there

A break in the sensor loop can be a loose connector, a failed sensor or a board input, and only a circuit test tells them apart.
An open reading that appears only when the oven warms up points to a connection that moves with heat.
We give a written price for the exact repair before we start.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

→Same appliance

Other Microwave codes

F8E5Whirlpool Microwave Code F8E5: Exhaust Air Temperature Sensor PUSH or PSHWhirlpool Built-in Microwave Shows PUSH or PSH: Press Start F9Whirlpool OTR Microwave Error F9: Control and Relay Boards Registration ErrorWhirlpool Over-the-range Microwave "Registration Error": Network Checks F9 or F9E0Whirlpool Built-in Microwave Codes F9 and F9E0: Home Power Supply Sabbath, Sab, 5Ab, or 5A6Whirlpool Built-in Microwave Showing Sab or 5Ab: Sabbath Mode F9QWhirlpool Over-the-range Microwave with F9Q on the Display: Power Reset Code SEWhirlpool Over-the-range Microwave Error SE: Keypad Circuit

E21E21 questions

What does an open thermal sensor circuit mean?

The control cannot complete the loop that reads temperature, as if a wire were cut. The cause can be the sensor, a connector or the board.

How is E21 different from E22?

E21 is an open circuit and E22 is a short in the same thermal sensor circuit. We test the circuit for both, since they point to the same area.

Will a reset cure E21?

It may clear a brief glitch. If E21 returns, the circuit has a lasting problem, and we test it and quote the repair in writing.

Book a visit

Still seeing E21?

A technician diagnoses it on site and gives you the price in writing before any work starts.

(713) 589-6107