Safety first: Unplug the smoker before accessing internal components.

Locate the temperature sensor: Inside the cooking chamber, find the small metal probe or bulb protruding from the wall. From the rear or bottom, trace its wires to the control board.
Inspect wiring and connector: Check for cuts, melted insulation, or pulled wires. Ensure the sensor plug is fully seated on the main control PCB. Reseat the connector several times to clear minor oxidation.
Visual sensor check: If the probe is bent, broken, or heavily corroded, it should be replaced. Do not attempt to straighten a cracked probe.
Replacement: Remove mounting screws or nut holding the sensor in place. Gently pull the sensor and harness through, then install the new Ninja-compatible NTC temperature sensor, routing the harness away from hot or sharp edges.
Test operation: Reassemble, plug in, and run a preheat cycle. If E04 remains, the fault may be on the control board’s sensor input circuit, requiring board replacement.

Smoker shows E04 and will not heat; fan and display may still operate.

Possible Causes