Toyota 89420-06040 Sensor Assembly, Vacuum

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The Manifold Absolute Pressure (MAP) sensor plays a crucial role in monitoring intake manifold pressure changes and converting them into a voltage output. This information is utilized by the Powertrain Control Module (PCM) to control fuel delivery and ignition timing. The voltage signal received by the PCM from the MAP sensor ranges from 1.9 to 2.1 volts at closed throttle (high vacuum) and 0.3 to 0.5 volts at wide open throttle (low vacuum), with slight variations based on altitude. The MAP sensor is mounted on a bracket attached to the engine compartment firewall. To check the MAP sensor, start by examining the reference voltage from the PCM. Disconnect the MAP sensor harness connector and measure the voltage between terminal 3 and terminal 1 (not the MAP sensor side) with a voltmeter. The reference voltage should read around 4.5 to 5.5 volts with the ignition key turned ON. If there are issues with the reference voltage, check the PCM. Next, simulate operating conditions by reconnecting the MAP sensor connector and back probing terminal 2 with the positive probe and terminal 1 with the negative probe. Disconnect the vacuum hose, connect a handheld vacuum pump, and apply the vacuum while observing the voltage increase on the signal wire. For MAP sensor replacement, ensure the ignition key is in the OFF position. Disconnect the electrical connector and vacuum hose from the MAP sensor. Remove the retaining bolt securing the MAP sensor to the firewall, and then take out the MAP sensor. To install the new MAP sensor, follow the reverse order of removal.