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Home >> Nissan-Datsun >> 2003 >> Frontier Base, Automatic >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0125: Engine Coolant Temperature Sensor >> Diagnostic Procedure
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Diagnostic Procedure

  1. Turn ignition off. Disconnect ECT sensor harness connector. See Figure or Figure . Turn ignition on. Measure voltage between ground and ECT sensor harness connector terminal No. 1 (Light Green/Red wire). If voltage is about 5 volts, go to step  3 . If voltage is not about 5 volts, go to next step.
  2. Repair open or short in Light Green/Red wire between ECM and ECT sensor.
  3. Turn ignition off. Check continuity between engine ground and ECT sensor harness connector terminal No. 2 (Black/White wire on 2.4L models; Brown wire on 3.3L models). Continuity should exist. Also, check circuit for short to voltage. If problem is found, repair as necessary. If problem is not found, go to next step.
  4. Remove ECT sensor, and place in heated water. Measure resistance between sensor terminals, with water at specified temperatures. See ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE  table under DIAGNOSTIC PROCEDURE under DTC P0117: ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT LOW INPUT OR DTC P0118: ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT HIGH INPUT  . If resistance is as specified, go to next step. If resistance is not as specified, replace ECT sensor.
  5. Reconnect all harness connectors. Allow engine to cool to less than 170°F (76.5°C). Start engine. Grasp lower radiator hose. If coolant is flowing through lower radiator hose, replace stuck open thermostat. If coolant is not flowing through lower radiator hose, go to next step.
  6. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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