GMC 12569240 Sensor,Map

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The Manifold Absolute Pressure (MAP) sensor monitors the intake manifold pressure changes resulting from changes in engine load and speed and converts the information into a voltage output. The ECM/PCM receives information as a varying voltage signal from closed throttle (high vacuum) to wide open throttle (low vacuum). The ECM/PCM uses the MAP sensor to control fuel delivery and ignition timing. Performing the following test will set a diagnostic trouble code and illuminate the Service Engine Soon light. Clear the diagnostic trouble code after performing the tests and making the necessary repairs. The MAP sensor is located on the upper intake manifold plenum. Check the terminals in the connector and the wires leading to the sensor for looseness and breaks. Repair as required. Before checking the MAP sensor, check the voltage supply and ground circuits from the ECM/PCM. Disconnect the electrical connector from the MAP sensor and connect the positive lead of a voltmeter to the gray wire terminal (and the negative lead to the orange/black or black wire terminal at the harness connector. Turn the ignition key On-the voltage should read approximately 5.0 volts. If the voltage is incorrect, check the wiring from the MAP sensor to the ECM/PCM. If the circuits are good, have the ECM/PCM checked at a dealer service department or other properly equipped repair facility. To check the MAP sensor operation, reconnect the connector to the MAP sensor and using a suitable probe, back probe the light green wire terminal of the MAP sensor connector. Connect the positive lead of a voltmeter to the probe and the negative lead to a good engine ground point. Turn the ignition key On-with the engine not running the voltage should read 4.0 to 5.0 volts. Start the engine and allow it to idle. The voltage should decrease to approximately 0.5 to 2.0 volts. If the test results are incorrect, replace the MAP sensor. Access the MAP sensor. On TBI systems, remove the air cleaner assembly. On Central SFI systems, remove the intake air duct and resonator from the throttle body. On MPFI systems, remove the upper intake manifold from the engine. Disconnect the electrical connector from the MAP sensor. Remove the retaining bolts and draw the MAP sensor. Replace the MAP sensor seal in the upper intake manifold, if equipped. Installation is the reverse of removal.

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 PCM sends a 5 volt reference signal to the MAP sensor and monitors the sensor output voltage to determine the manifold pressure.