Chevrolet 12569240 Sensor,Map

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

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.

The checking procedures for various engine sensors and components are as follows: The engine coolant temperature (ECT) sensor is a thermistor that changes resistance with temperature, and a failure in the circuit can trigger trouble codes. To check it, measure the resistance while cold and warm, and ensure the reference voltage from the PCM is around 5.0 volts. The manifold absolute pressure (MAP) sensor monitors intake manifold pressure changes and varies its voltage output accordingly. Check the reference voltage and signal voltage with the ignition on and engine off, and observe voltage changes as the engine's vacuum changes. The intake air temperature (IAT) sensor acts as a thermistor, and you can measure its resistance at different temperatures to ensure it changes as expected. Also, monitor the IAT sensor using a scan tool to verify its performance. The oxygen sensor in the exhaust monitors oxygen content, and you can check its millivolt signal while the engine warms up. Inspect the oxygen sensor heater and ensure it receives proper voltage. The vehicle speed sensor (VSS) provides speed data to the PCM and can be checked for reference voltage. The camshaft sensor and crankshaft sensor, depending on the engine type, should be checked for resistance and proper signal output. Finally, the knock sensors detect engine knock and should be checked for reference voltage and resistance. If any component fails these checks, replacement may be necessary.