Test NTC-12: Checking Engine Coolant Temperature Sensor

NOTE: For circuit identification, see WIRING DIAGRAMS article. After each repair procedure has been completed, reconnect all components. Perform TEST VER-5 to ensure system is functioning properly. Ensure no DTCs are present before performing this test.

NOTE: To perform the following test, manufacturer recommends allowing vehicle to sit overnight in order to have a totally cold engine.

Turn ignition off. Visually inspect related connectors and wiring harness for damage. Repair connectors and wiring harness as necessary. If connectors and wiring harness are okay, reconnect all connectors. Start engine. Wiggle Engine Coolant Temperature (ECT) sensor connector and wiring harness while monitoring scan tool display. If GOOD TRIP counter display count changes to "0", repair connector or wiring harness where wiggling caused display to change. If GOOD TRIP counter display count does not change to "0", go to next step.
NOTE: For the following step to be valid, thermostat must be functioning properly.
Turn ignition on. Using scan tool, read ENG COOLANT TPM DEG value. If engine was allowed to sit overnight, scan tool temperature value should be near ambient air temperature. If engine coolant temperature is more than 180°F (82.2°C), allow engine coolant temperature to cool down to 150°F (65.5.°C) before proceeding. If engine coolant temperature is 150°F (65.5°C) or less, start engine. Using scan tool, monitor ENG COOLANT TPM DEG. Temperature value should increase smoothly from start-up to normal operating temperature. Temperature should reach at least 180°F (82.2°C). If temperature increases smoothly and reaches at least 180°F (82.2°C), no problem is indicated at this time. Test is complete. If temperature does not increase smoothly or does not reach 180°F (82.2°C), replace ECT sensor.