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Hey guys, does anyone happen to know the typical range of the “Induction System Leak Indication” at idle on a 2015 Chevrolet Silverado 2500HD with LML Duramax? I’m getting a ratio of 0.61:1. Does this mean I’m getting more or less air than what the MAF is reading? The truck is also not building boost like it should. Any help is appreciated.
Hey BobRoss! I got this from a training class I went to several years ago:
Less than .90:1 - Measured airflow too low due to leaks between the MAF and turbo inlet (i.e. unboosted intake) or MAF miscalibration. Can also be caused by a failed turbo, exhaust leaks between the exhaust manifolds and the turbo, or EGR flow (not seating).
More than 1.10:1 - Measured airflow too high due to MAF miscalibration or leaks in the boosted side of the intake. Free- flowing exhaust can also reduce this ratio (increase flow).
There's also PIP4932D which says pretty much the same thing:
Remember that the ALER/ASLI/ILSI reading is only valid if the EGR valve is closed. Was your reading of .61:1 with the EGR valve closed? If not, that might be part of the problem. Close the EGR and recheck your reading.
Thanks for the information! I will command the EGR closed and check the ISLI again. I suspect the leak may be on the unboosted intake like you mentioned because my last used oil analysis showed elevated iron levels. Is there a standard method used to find the leak on the unboosted side? Thanks for the help!
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