GMC 10456146 Sensor,Knock

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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.

The knock sensor is responsible for detecting abnormal engine vibrations and reducing spark knock. It produces an AC output voltage that increases with the severity of the knock, which is then fed into the ECM/PCM to retard the timing.

To test the sensor's operation, reconnect the connector and use a voltmeter to check for an AC voltage signal while the engine is running. The voltage should increase as the engine speed increases. If no voltage signal is present, the knock sensor should be replaced.

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

The oxygen sensor in the exhaust monitors oxygen content. To check it, you can check its millivolt signal while the engine warms up. It is also important to inspect the oxygen sensor heater and ensure it receives proper voltage.

The manifold absolute pressure (MAP) sensor monitors intake manifold pressure changes and varies its voltage output accordingly. To check it, you should check the reference voltage and signal voltage with the ignition on and engine off, and observe voltage changes as the engine's vacuum changes.