ECT Switch Testing

WARNING: Removing the ECT switch while the engine is hot can cause the coolant to spray out, seriously scalding you. Always let the engine and radiator cool down before removing the ECT switch.

NOTE: Bleed air from the cooling system after installing the ECT switch (see ENGINE COOLANT REFILLING AND BLEEDING ).

Remove the ECT switch from the thermostat cover (see THERMOSTAT ).
Suspend the ECT switch in a container of water as shown.

Fig 1: Identifying ECT Switch In Container Of Water
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Heat the water and check the temperature with a thermometer.
CAUTION: Do not let the thermometer touch the bottom of the hot container.
Measure the continuity between the A and B terminals according to the table.

Fig 2: Measuring Continuity Between A And B Terminals
Courtesy of AMERICAN HONDA MOTOR CO., INC.