Cadillac 12559850 Sensor,Heated Oxygen

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Various engine sensors and components have checking procedures,the engine coolant temperature (ECT) sensor is a thermistor that changes resistance with temperature, and a failure in the circuit can cause trouble codes. The resistance should be measured when cold and warm while ensuring reference voltage from PCM is around 5.0 volts for the verification. Manifold Absolute Pressure (MAP) Sensor monitors changes in intake manifold pressure then varies its voltage output accordingly. Look at the reference voltage and signal voltage with the ignition on and engine off, and observe voltage changes as the engine's vacuum changes. Intake Air Temperature (IAT) Sensor acts as a thermistor where you can measure its resistance at different temperatures to make sure it changes as expected. Also, use a scan tool to monitor the IAT sensor for performance. The oxygen sensor in exhaust detects oxygen content which you can check its millivolt signal while warming up your engine. Check whether the oxygen sensor heater has correct voltage or not. Vehicle Speed Sensor (VSS) provides speed data to PCM which can be checked for reference voltage. Depending on the type of engine, Camshaft Sensor and Crankshaft Sensor should be checked for resistance and proper signal output. Finally, Knock Sensors detect engine knock which should be checked for reference voltage and resistance. If any component fails these checks, replacement may be necessary.

When servicing the oxygen sensor, the permanently attached pigtail and connector should not be removed. Grease, dirt, and other contaminants should be kept away from the electrical connector and the louvered end of the sensor. Cleaning solvents should not be used on the oxygen sensor. The sensor should not be dropped or roughly handled. The silicone boot must be installed correctly to prevent melting and ensure proper operation.

The knock sensors detect engine knock. To check them, you should check for reference voltage and resistance.

The engine coolant temperature (ECT) sensor is a thermistor that changes resistance with temperature. To check it, measure the resistance while cold and warm, and ensure the reference voltage from the PCM is around 5.0 volts.