ECT Sensor Circuit Troubleshooting

2008 Acura MDXSECTION ECT Sensor Circuit Troubleshooting
WARNING: This page is about a different car, the 2006 Acura MDX, 2005 Acura MDX, 2004 Acura MDX, and 2003 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check the malfunction indicator lamp (MIL).

    Does the malfunction indicator lamp come on? 

    1. YES  - Refer to the powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ).
    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 (26P).
  5. Turn the ignition switch ON (II).
  6. Measure the voltage between the No. 22 terminal of climate control unit connector B (26P) and body ground.
    Fig 1: Measuring Voltage Between No. 22 Terminal Of Climate Control Unit Connector B And Body Ground
    G03641848Courtesy 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 (26P) 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.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.