Toyota 22204-07010 Meter Sub-Assy, Intake Air Flow

The Mass Airflow (MAF) sensor is located on the air intake duct and consists of a platinum hot wire, a thermistor, and a control circuit housed in plastic. This system detects temperature changes in the intake air through the hot wire and thermistor. As the throttle opens, more air flows over the hot wire, causing it to cool. The MAF sensor circuit adjusts the current flow through the hot wire to maintain a constant temperature. The PCM measures the output voltage signal from the MAF sensor, converts it into a digital waveform, compares it to the map, calculates the required fuel injector pulse width, and controls the injectors accordingly. Any issues with the MAF sensor circuit will trigger a diagnostic trouble code. To check the MAF sensor, verify power to the sensor and test for battery voltage. Assess the MAF sensor voltage signal to the PCM by reconnecting the electrical connector and observing the voltage while the engine idles and varies in speed. If the signal voltage is out of range, inspect the wiring harness for damage or connection problems. If the wiring and connectors are intact, it is likely that the MAF sensor is faulty. Before replacing the MAF sensor, check the circuit due to its high cost. For MAF sensor replacement, ensure the ignition key is in the OFF position and disconnect the electrical connector. Remove the sensor by loosening the retaining bolts and removing it along with the gasket. Installation involves reversing the removal steps and ensuring the installation of a new gasket between the MAF sensor and the intake duct.

As the wire cools, the Powertrain Control Module (PCM) increases the flow of current through the hot wire to maintain it at a constant temperature.

A problem in the MAF sensor circuit will set a diagnostic trouble code.