They range in price but are rarely expensive. There are a variety of VE calculators available for PC’s, smart phones and more. At this point we will note the engine RPM (6107) and the MAF (104.62 g/sec) readings and apply them to a VE calculation. Engine load will be addressed next.Īfter the test drive has been recorded, a cursor is placed near the peak of the RPM trace which I have placed at the top of the image.
In this case (Figure 4) I have chosen to add the engine load PID as well. There may be other data PID’s that you want to observe also. The scan data that you will need to record should include: engine RPM, Mass Airflow (g/sec) and oxygen sensor voltage at a minimum. It is a very dynamic test that is performed by recording scan data during a wide-open throttle test drive. Volumetric efficiency, or VE, is my preferred method for testing Mass Airflow sensors. In the recording we achieved 104 grams per second which is definitely acceptable. That means that our airflow measurement should exceed 80 grams per second or 2.0 times 40. In this case, a test drive was recorded (Figure 3) on a 2.0-liter engine. The peak MAF reading should exceed forty times the engine’s displacement. Take the vehicle on a wide-open throttle test drive and record the MAF sensor signal in grams per second. The forty times rule is relatively simple. As a result, I do not use this test very often. This is due to the PCM controlling the throttle movement. The peak voltage only reaches about 3 volts. The MAF capture shown is from a vehicle with ETC and does not have a MAF sensor issue. Quite often the PCM will not open the throttle fast enough to achieve the initial gulp of air required for this test’s accuracy. However, there is a flaw with this test when used on a vehicle with electronic throttle control. On a vehicle with a cabled throttle this test works quite well. Observe the voltage level at the first peak (Figure 2.) A general rule of thumb is voltage should exceed 4 volts. With the vehicle in park, snap the throttle wide open as fast as you can. To perform the test, connect a scope to the MAF sensor signal wire. The analog style signal is what applies here. Others output a digital square wave signal and the PCM measures the frequency of that signal. What I mean by that is some sensors output a 0 to 5-volt analog signal. This test is only useful on an analog style MAF sensor. Snap The ThrottleĪnother test that can help is a snap throttle test with a scope. If this test fails there could be an airflow issue but MAF sensors could still pass this test and be faulty. This is exactly two times the engine displacement. When the engine returned to idle the MAF reading is 4.00 grams per second. In the following example (Figure 1) I snapped the throttle a few times on a 2.0 liter naturally aspirated Ford product. The way it works is: at idle the engine should draw approximately two times the engine displacement in grams per second. It will alert you to a gross MAF failure but nothing more. The double the displacement rule is a mediocre test. I am putting my foot down… this test is basically worthless. Some modern vehicles will not even run with the MAF sensor disconnected.
#MAX AIRFLOW SENSOR SOFTWARE#
Modern vehicles have software strategies that render this technique useless. If we were working on a 1986 Pontiac 6000 that may have been acceptable. I have been in this industry for many years and I can say that unplugging a MAF sensor used to be a good tactic. Regardless, there are multiple ways to test MAF sensors and I will do my best to go through them all. In other cases, a failed MAF sensor will cause lean codes such as P0171 or P0174. In addition, mass air flow sensor issues usually present themselves as a drivability problem with no DTC or MIL illumination. During diagnosis mass air flow sensor codes are usually an indication of another underlying problem. MAF sensors are one of the most common “Shotgun” parts that technicians swap. It can affect fuel delivery, transmission shifting and more. Air flow measurement is a HUGE input on Mass Airflow sensor (MAF) equipped vehicles. If you did not know, the engine has to be operating properly before we can diagnose transmission problems.
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