Testing the vane air flow (VAF) sensor of the 1992-1993 3.0L Toyota Camry can be done easily and accurately using only a multimeter.
That's right, you'll be able to find out if the vane air flow sensor is defective or not.
NOTE: I'll be referring to the vane air flow sensor as the MAF sensor in this tutorial.
Contents of the tutorial at a glance:
- MAF Sensor Basics.
- Circuit Descriptions Of The MAF Sensor.
- 1992-1993 3.0L Toyota Camry MAF Sensor Test Summary.
- TEST 1: Making Sure The MAF Sensor Is Getting Power.
- TEST 2: Making Sure The MAF Sensor Is Getting Ground.
- TEST 3: Testing The MAF Signal With A Multimeter.
MAF Sensor Basics
This is a brief summary of the performance test of the Toyota vane air flow sensor that you'll be performing in this article. This is a very easy and simple test but there are a couple of things that have to be done first. The two most important are:
- Verify that the engine does not have any vacuum leaks.
- Verify that there are no ignition system misfires. A misfire condition will skew the results of the test you'll perform here.
If the above conditions exist, repairing them first will more than likely solve your vehicle's drive-ability issue without having to test the MAF sensor, if not continue with the MAF sensor test in this article.
Alright, the most common symptoms of a bad MAF sensor are:
- A MAF sensor code.
- A tremendous lack of power upon acceleration.
- Black smoke coming from the tail-pipe.
- Vehicle may idle rough and stall.
Circuit Descriptions Of The MAF Sensor
To test the vane air flow signal, the vane air flow sensor needs to be connected to its connector. This means you have to connect your multimeter's probe to a back-probe or a wire piercing probe (you can see an example of this tool here: Wire Piercing Probe).
Independent of the method you use, be careful not to damage the signal wire. Take all safety precautions.
IMPORTANT: All of the tests are ON CAR TESTS, do not remove the vane air flow meter from the vehicle or from its plumbing.
You'll notice that in the photo above the VAF connector is numbered 1 thru 7. The only circuits that we are going to be concerned about (to test the VAF sensor) are circuits number 4, 5, and 6. Here's the description of each circuit below.
- Number 1- Fuel pump switch circuit.
- Number 2- Fuel pump switch circuit.
- Number 3- Empty slot on connector. No circuit exists.
- Number 4- 5 V Reference from ECM.
- Number 5- Sensor Ground thru' the ECM (Fuel Injection Computer).
- Number 6- VAF Signal.
- Number 7- Air Temperature Sensor Circuit.
1992-1993 3.0L Toyota Camry MAF Sensor Test Summary
We're gonna' start off by checking the basics. These are 5 Volts and Ground to the vane air flow sensor. After that, we'll test the actual performance of the VAF sensor as the engine is running.
I recommend using a digital multimeter for all tests where a multimeter is called for. Why? -you may ask. Only a digital multimeter will be able to keep up with and register the output signal of the VAF sensor.
The vane air flow sensor signal is directly related to amount of air the engine is breathing. The more air the engine breathes, the SMALLER the voltage that the sensor produces. This sensor works the opposite of most mass air flow sensors whose signal increases with increased air flow.
Common sense tells us that the engine will breathe in more air at 2500 RPMs than at an idle of 900 RPMs. So keeping this in mind, the voltage value on the multimeter will be smaller at 2500 RPM than at 900 RPM.
Now, when testing this voltage output signal, the important thing to know is not an actual voltage number at a specific RPM, but to confirm that the voltage value actually decreases as you accelerate the engine. If the voltage value does not decrease as you're accelerating the engine, then the vane air flow meter is defective.
Lastly, these tests are not designed to diagnose an intermittent problem with the VAF sensor. They are designed to diagnose a hard fault with the sensor.