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You have a P0171, what in the real world is likely going on? Vacuum leaks, air-fuel sensors pinned lean and bad MAF sensors are the common culprits. So you get a 2006 Toyota Corolla and it has a P0171.
You can use an ATS EScan scan tool, which has a built in volumetric efficiency test, or go to Google and use a volumetric efficiency calculator. An even quicker method is to go wide open throttle (WOT) while looking at the Calculated Load PID in Generic OBDII on your scan tool. If it is lower than 90 percent inspect the MAF. It is common on these Corollas that they are contaminated, so it is good to replace them. We have not had success cleaning these sensors on several vehicles.
You can confirm this two ways. The easy way is to smoke the intake with CO2 gas and use an emissions analyzer to find if you have elevated CO2 levels around the intake manifold as compared to atmospheric CO2. Otherwise, just pull the intake off. What you will find is that the original gaskets flatten and the new replacement gasket is much more robust.
This will solve your P0171, but without the right tools (scan tool, emissions analyzer, smoke machine) you will never be able to catch this fault (see Figures 4 and 5).
2008 Hyundai Accent ‘Invisible Misfire’ Many Hyundai Accents have a P0300 or other misfire DTCs,Still in Figure 6, a 2008 Hyundai Accent is hooked up for a reflash. A battery maintainer should always be used.
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