Diagnostic Aids

Use scan tool to review malfunction history diagnostic information. This data can be used to duplicate intermittent problems. Check tightness of harness connector terminals.

Start engine and observe ECT reading on scan tool. ECT reading should rise smoothly to about 190°F (88°C) as thermostat opens and then stabilizes. PCM will turn on cooling fan if an ECT DTC is set.

ECT temperature can be compared to IAT temperature with scan tool, if engine has cooled overnight at ambient temperature. ECT and IAT temperatures should be within 4 degrees of each other with ignition on, engine off. See appropriate SENSOR OPERATING RANGE CHARTS article.