Note. Dark exhaust smoke or an inadequate fast idle speed during engine warm-up may be caused by a faulty Engine Coolant Temperature (ECT) sensor.
- Turn ignition on. Install scan tool to data link connector, and verify DTC P0115, P0116 or P0125 is set. If DTC P0115, P0116 or P0125 is set, go to next step. If DTC P0115, P0116 or P0125 is not set, ensure ECT sensor and ECM connectors are clean and tight. Perform repairs as necessary. When repairs are completed, clear DTCs and verify ECT sensor operation.
- Turn ignition off. Disconnect ECT sensor connector. Check for continuity between ground and ECT sensor connector terminal No. 1 (Black/White wire). If continuity exists, go to next step. If continuity does not exist, repair open in Black/White wire between ECT sensor and ECM. If Black/White wire is okay, replace ECM. When repairs are completed, clear DTCs and verify ECT sensor operation.
- Turn ignition on. Measure voltage between ground and ECT sensor connector terminal No. 2 (Green wire). If voltage is 4.5-4.9 volts, go to next step. If voltage is not 4.5-4.9 volts, repair open or short in Green wire between ECM and ECT sensor. When repairs are completed, clear DTCs and verify ECT sensor operation.
- Turn ignition off. Reconnect ECT sensor connector. Start engine and allow to idle. Monitor engine coolant temperature using an external thermometer. Backprobe ECM connector, and measure voltage at ECM connector 44-2 (A/T) terminal No. 3 (Green wire) or connector 45-4 (M/T) terminal No. 21 (Green wire) as coolant temperature changes. See «ETC SENSOR SPECIFICATIONS»(ref-89280-S01725438672001022800000) table. If ECT sensor output voltage is approximately as specified, go to next step. If output voltage is not as specified, replace ECT sensor. When repairs are completed, clear DTCs and verify ECT sensor operation.
- Turn ignition off. Carefully remove ECT sensor. With sensing portion of ETC sensor immersed in cool water, check resistance as water is heated. See «ETC SENSOR SPECIFICATIONS»(ref-89280-S01725438672001022800000) table. If ECT sensor resistance is approximately as specified, go to next step. If ECT sensor resistance is not approximately as specified, replace ETC sensor. When repairs are completed, clear DTCs and verify ECT sensor operation. ECT SENSOR SPECIFICATIONS Temperature °F (°C) Ohms Output Voltage 32 (0) 5900 4.05 68 (20) 2500 3.44 104 (40) 1100 2.72 176 (80) 300 1.25
- Check cooling system, including thermostat. Perform repairs as necessary. If cooling system is okay, clear DTC P0115. Retest system. If DTC P0115 does not reset, system is okay. If DTC P0115 resets, replace ECM.