A sensor-operated toilet that never starts a flush needs activation, power and water-supply conditions separated before a diaphragm is replaced. Identify the exact controller, record indicators and whether its intended manual control works, and follow its troubleshooting table. A dirty lens, recognition fault, disrupted power or closed supply can have different remedies; internal electrical and valve work needs qualified service.
Record the exact behavior
A toilet that does not activate at all presents a different problem from one that activates but flushes weakly. Start by identifying the valve and controller rather than assuming the hydraulic rebuild kit is the answer. Automatic sensing and water delivery are separate parts of the system.
Note the model, available indicator pattern, whether any flush begins, and whether the problem affects one fixture or the whole restroom. If the unit has an owner-accessible manual control, record its response according to the actual instructions. Do not improvise an activation by shorting wires or moving internal actuator parts.
For a cycle that starts but fails to clear the bowl, see a weak commercial flushometer flush. This page concerns initiating the cycle.
Check recognition without changing the system
Zurn's cited ZEMS-series instructions list a dirty lens, a reflective surface in front of the sensor, incorrect detection range and component faults among activation problems. The separate ZEMS-IS troubleshooting guide also identifies failure to recognize the user.
Clean the exterior only by the maker's permitted method. Zurn calls for mild soap and water on chrome and protection of the lens from cleaning chemicals. Record a new door, partition or reflective object near the sensing area. Do not cover the sensor or change its range by following another model's calibration sequence.
Distinguish controller power from water supply
Both cited Zurn documents discuss disrupted power and closed supply conditions. Their electrical details apply to the listed hardwired equipment, not a universal battery replacement instruction for every sensor valve.
Have qualified personnel evaluate power, controller connections and actuator operation using the correct manual. An LED or an audible movement is a useful observation, not proof that every power and actuator requirement is satisfied. Do not open a wall escutcheon for live voltage tests.
If a control stop or building supply was changed during maintenance, report that history. Do not force a valve or open it without regard to what the fixture can safely drain. A supply fault cannot be corrected by recalibrating the lens.
Verify the complete operation after repair
Once the identified cause is corrected, check recognition, the actual flush and shutoff together under the model's instructions. A continuously running flushometer has another hydraulic investigation.
Record the exact repaired part, settings and remaining symptoms in the commercial maintenance plan. A single successful activation does not establish that an intermittent fault or a shared supply problem is resolved.