What E21 Means
JennAir's E21 page says the thermal sensor circuit reported open to the control board, and names the thermal sensor, the appliance control board, or the associated wiring. An open circuit means the control is seeing no signal at all rather than a wrong one.
Common Causes of E21
- A thermal sensor that has gone open circuit
- A broken sensor lead or an unplugged connector
- An appliance control board no longer reading the sensor input
🔧 One Safe Check You Can Try
Reset at the breaker for a minute and restore power, then note whether the code returns immediately or only when a heating function is selected.
⚠ Why You Shouldn't Go Further Than That
- An open circuit is often a connector rather than a part, and that distinction is only visible with continuity checks on a fully isolated appliance.
- The sensor leads run through the hot section of the unit, where insulation ages and cracks as soon as it is disturbed.
- Working inside an over-the-range microwave means working next to a capacitor that stores a lethal charge after the plug is pulled.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.
Technical Reference
- Code
- E21
- Appliance
- JennAir microwave
- Maker documentation
- JennAir owner manuals and use & care guides
- Checked
- September 2026
Code meanings can change between control generations. Before acting on a code, match the full model number on your appliance's rating label against the manual for that model. We are an independent repair service, not affiliated with Whirlpool Corporation.