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Diagnosis & Repair Procedure

NOTE: For better performance and results of this diagnostic procedure, usage of appropriate wiring diagram is recommended. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
NOTE: Perform all voltage and resistance tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use an ohmmeter to isolate wiring harness shorts or opens.
  1. If engine system check has been performed, go to next step. If engine system check has not been performed, perform A-4: ENGINE SYSTEM CHECK  under SYSTEM TESTS, then go to next step.
  2. Turn ignition switch to ON position. Using scan tool, observe and record ECT sensor value. If ECT sensor value is -40°F (-40°C), go to next step. If ECT sensor value is not -40°F (-40°C), problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. After repair, repeat DTC CONFIRMATION TEST  .
  3. Turn ignition switch to LOCK position. Disconnect ECT sensor 3-pin harness connector C10, located on water outlet cap, at rear of engine. See Figure . Check ECT sensor and harness connector terminals for corrosion or poor connection. If connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST  . If connector terminals are okay, turn ignition switch to ON position and measure voltage between ground and ECT sensor harness connector C10 terminal No. 1 (Orange/Black wire). See Figure . If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, check for open or short circuit in Orange/Black wire between ECM and ECT sensor. If open or short circuit is found, repair as necessary and DTC CONFIRMATION TEST  . If open or short circuit is not found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST  .
  4. Ensure ignition switch is in ON position. Using scan tool, observe ECT sensor values. If ECT sensor values display on scanner is 327°F (164°C), replace ECT sensor. See ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL & INSTALLATION article. After repair, repeat DTC CONFIRMATION TEST  . If ECT sensor values display on scanner is not 327°F (164°C), check for open or short circuit in Orange/Black wire between ECM and ECT sensor. If open or short circuit is found, repair as necessary and DTC CONFIRMATION TEST  . If open or short circuit is not found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST  .
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