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ECA 4 - Code 09 (Coolant Temperature Sensor)

  1. Check for loose connectors, corrosion or damage at coolant temperature sensor and ECA terminal 2I. Repair as necessary.
  2. Check resistance across temperature sensor terminals. Resistance should be as shown in COOLANT TEMPERATURE SENSOR RESISTANCE  table. If resistance is incorrect, replace temperature sensor.
    COOLANT TEMPERATURE SENSOR RESISTANCE

    Coolant Temperature Ohms
    -4°F (-20°C) 14,600-17,800
    68°F (20°C) 2210-2690
    176°F (80°C) 290-354
  3. If resistance is within specification, turn ignition on and check for voltage at ECA terminal 2I. If voltage reading is 5 volts, check for open in wire between temperature sensor Brown/Red terminal and ECA terminal 2I. Repair as necessary.
  4. If voltage reading is 0-2.5 volts, check for short in wire between temperature sensor Brown/Red terminal and ECA terminal 2I. Repair as necessary.
  5. If no short is indicated, go to ECA 8  . If symptom persists, go to ECA 55  .