Posted to Technical Tips Forum on 6/6/2012
32 Replies
There has been a number of methods that have been discussed
for testing underreporting MAF sensors. Certainly having
more then one method to test a MAF sensor adds extra tooling
in your tool box. Here is a method I have found to work very
well when checking a MAF sensor. This method is used once
you have done some preliminary diagnosis and you are
speculating you might have a skewed MAF sensor. The test
involves graphing 2 Pids (STFT-Short term fuel trim) and
(RPM) the test is done during light cruise speeds at gentle
throttle tip In's below 3000 rpm. While monitoring the
graphed data pids if the Short term fuel trim is mirroring
the RPM I have found this indicates a skewed MAF sensor and
will require replacement as this example shows
[2001 Toyota Camry LE, ECM/Inputs/Outputs Scan Data]
here is another example
[2001 Toyota Camry LE, ECM/Inputs/Outputs Scan Data]
Keep in mind the throttle tip In's must be made below
approx. 3000 rpm otherwise the mirroring effect between the
2 pids will not mimic one and other. Here is an example of
why this test must be done below 3000 RPM.
[2001 Toyota Camry LE, ECM/Inputs/Outputs Scan Data]
This method is a quick and simple testing procedure and I
have found it simply allot faster then using a VE calculator
and/or graphing numerous pids to examine after a test drive.
However please remember using those other methods along with
this one can certainly aid in conclusively determining if
you have a skewed maf sensor... consider this method as
adding another tool to the tool box.
Here is the after capture on the above vehicle with a new
Toyota MAF sensor
[2001 Toyota Camry LE, ECM/Inputs/Outputs Scan Data]
Kevin from Manitoba
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