ECT Sensor Circuit Troubleshooting

Check the malfunction indicator lamp (MIL).
Does the malfunction indicator lamp come on ?
1. YES : Refer to fuel and emissions (see SELF-DIAGNOSTICS ).
2. NO : Go to step 2.
Turn the ignition switch OFF.
Disconnect the ECT sensor 2P connector (see COMPONENT LOCATIONS ).
Disconnect climate control unit connector B (20P).
Turn the ignition switch ON (II).
Measure the voltage between the No. 3 terminal of climate control unit connector B (20P) and body ground.

Fig 1: Measuring Voltage Between The Climate Control Unit Connector B (20P) And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there about 5 V ?
1. YES : Check for loose wires or poor connections at climate control unit connector B (20P) and at the ECT sensor 2P connector. If the connections are good, substitute a known-good climate control unit, and recheck. If the symptom/indication goes away, replace the original climate control unit.
2. NO : Repair open in the wire between the climate control unit and the ECT sensor.