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, perform A-4: ENGINE SYSTEM CHECK under SYSTEM TESTS, then 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. See Figure . 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. See ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL & INSTALLATION article. After repair, repeat DTC CONFIRMATION TEST .