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.

If engine system check has been performed, go to next step. If engine system check has not been performed, see and perform A-4: ENGINE SYSTEM CHECK under SYSTEM TESTS and go to next step.
Turn ignition switch to ON position. Using scan tool, observe and record ECT sensor value. If ECT sensor value is 327°F (164°C), go to next step. If ECT sensor value is not 401°F (205°C), problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO-CODES article. After repair, repeat DTC CONFIRMATION TEST .
Turn ignition switch to LOCK position. Disconnect ECT sensor 3-pin harness connector C10, located on water outlet cap, at rear of engine. Turn ignition switch to ON position. Using scan tool, observe ECT sensor values. If ECT sensor values display on scanner is -40°F (-40°C), replace ECT sensor. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION article. After repair, repeat DTC CONFIRMATION TEST . If ECT sensor values display on scanner is not -40°F (-40°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 .