How to Test Automotive Sensors: MAF, O2, and TPS

Modern vehicles rely on a network of sensors to manage engine performance. When a Check Engine Light (CEL) comes on, testing these sensors before replacing them can save you hundreds of dollars.

Mass Air Flow (MAF) Sensor

The MAF sensor measures the amount of air entering the engine. To test it, check the signal wire voltage with a multimeter while the engine is idling. Rev the engine; the voltage should rise smoothly. Erratic jumps indicate a fault.

Oxygen (O2) Sensor

O2 sensors monitor exhaust gases. A healthy upstream O2 sensor should oscillate rapidly between 0.1V and 0.9V. If it stays stuck or moves slowly, it is likely lazy or dead.