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 (ECT sensor 1 - engine cold). Start engine and allow it to reach normal operating temperature, observe and record ECT sensor value (ECT sensor 2 - engine warm). If difference value between ECT sensors is more than 2°F (1°C), go to next step. If difference value between ECT sensors is less than 2°F (1°C), go to step 4 .
- Check thermostat operation, by observing if heater takes a long time to become effective, or coolant flows into radiator on cold start. Thermostat should begin to open at 175.4-182.6°F (79.7-83.7°C). Thermostat should be completely open at 212°F (100°C). Thermostat valve should lift to more than 51/64" (8 mm) at 203°F (95°C). If thermostat is operating okay, go to next step. If thermostat is faulty, replace thermostat. 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 while connecting fused jumper wire between ECT sensor harness connector C10 terminals No. 1 (Orange/Black wire) and No. 3 (Blue/White wire). See Fig 1 . Temperature displayed on scan tool should be 327°F (164°C). Also check ECT sensor values with fused jumper wire disconnected. Temperature displayed on scan tool should be now 40°F (-40°C). If temperature values are as specified, go to next step. If temperature values are not as specified, 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 .
- Turn ignition switch to LOCK position. Perform ECT sensor component test. See ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article. If ECT sensor is okay, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO-CODES article. After repair, repeat DTC CONFIRMATION TEST . If ECT sensor is faulty, replace ECT sensor. After repair, repeat DTC CONFIRMATION TEST .