Controller shows E05 and pump runs only at low speed or not at all.

Safety: Isolate the pump at the main isolator before testing any wiring.

• Inspect sensor cable: Trace the motor temperature sensor cable from the motor terminal box to the Certikin controller. Look for cuts, crushed sections, or loose plugs. Reseat any connectors.
• Test sensor continuity: Disconnect the sensor leads and measure resistance with a multimeter. An open circuit or infinite resistance indicates a failed sensor.
• Check controller settings: In the controller menu (refer to the Certikin manual), confirm the correct sensor type (e.g. PTC, NTC) is selected.
• Bypass for testing only: Some controllers allow temporary bypass of the sensor for diagnostic purposes. This should only be done briefly and under supervision to avoid overheating.

If the sensor is faulty, replace it with the correct Certikin motor temperature sensor or replace the motor if the sensor is embedded and non-serviceable.