TEST 3: Testing The MAF Signal With A Multimeter
In this last test, we'll check the MAF signal coming out of the sensor and going to the fuel injection computer.
The wire labeled with the #6 arrow in the photo above is the one that carries the MAF signal to your Toyota Camry's fuel injection computer.
What we're looking for is for the MAF signal voltage to decrease when we accelerate the engine and for it to increase when decelerate the engine
What will tell you that your Toyota Camry's vane air flow sensor is defective will be that the MAF signal will stay stuck in one value as you accelerate the engine.
NOTE: To test the MAF signal, your Camry's vane air flow sensor must be connected to its electrical connector. You'll need to use a back-probe or a wire piercing probe to access the MAF signal. You can see an example of a wire piercing probe here: Wire Piercing Probe.
OK, let's get started:
Place your multimeter in Volts DC mode.
Probe the wire labeled with the #6 (see photo above) with the red multimeter test lead and an appropriate tool.
Connect the black multimeter probe to the battery negative (-) post.
Start the engine and let it idle for about 5 minutes till it reaches its normal operating temperature.
Accelerate the engine as you watch the multimeter's Volts DC readings.
The voltage reading should DECREASE when you accelerate the engine and should INCREASE when you decelerate it.
Let's interpret your test result:
CASE 1: The voltage readings decreased and increased as indicated. This is the correct and expected test result and tells you that the vane air flow sensor (on your Toyota Camry) is working correctly.
CASE 1: The voltage readings DID NOT decrease or increase as indicated. This test result tells you that the vane air flow meter on your Toyota Camry is defective and needs to be replaced.
If this info really saved the day, buy me a beer!