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, but the customer will report no obvious misfires. The vehicle in Figure 6 had a tune up with aftermarket spark plugs twice, never reporting a misfire. However, changing over to OE plugs did not fix this vehicle. There is a TSB that recommends updating the PCM software.
Still in Figure 6, a 2008 Hyundai Accent is hooked up for a reflash. A battery maintainer should always be used.
How would we do this for a Hyundai? It is an easy process. A J2534 reprogramming device (the Drewtech Cardaq is recommended), 32-bit laptop with Windows XP, and free subscription to Hyundaitechinfo.com is all that’s needed.
Here’s how you do it. We have found that doing such a reflash is a straightforward and error-free process as long as you follow the precautions you see in Figure 7. Otherwise, simply check that the Calibration ID is different than the old one and click OK (See Figure 8). The screen will look static as if nothing is happening, but wait a few minutes for the software to indicate when the reflash is done.
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