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ECT Sensor Circuit Troubleshooting

NOTE: Before performing symptom troubleshooting, check for powertrain DTC (see HOW TO USE THE HONDA DIAGNOSTIC SYSTEM (HDS) ).
  1. Check the malfunction indicator lamp (MIL).

    Does the malfunction indicator lamp come on? 

    1. YES  - Refer to the fuel and emissions systems DTCs (see HOW TO USE THE HONDA DIAGNOSTIC SYSTEM (HDS) ).
    2. NO  - Go to Step 2.
  2. Turn the ignition switch OFF.
  3. Disconnect the ECT sensor 2P connector.
  4. Disconnect climate control unit connector B (30P).
  5. Turn the ignition switch ON (II).
  6. Measure the voltage between the No. 22 terminal of climate control unit connector B (30P) and body ground.
    Fig 1: Measuring The Voltage Between The No. 22 Terminal Of Climate Control Unit Connector B (30P) & Body Ground
    G01465832Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there about 5V? 

    1. YES  - Check for loose wires or poor connections at climate control unit connector B (30P) 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.