Hi ! Up to this point there is not a specific answer. I drove into a regular station. My car was running rough, the mechanic show me a broken hose that runs from the valve cover, to the intake manifold. He also show me that the ignition coil on cylinder #4 was firing against the wall. The mechanic told me that those issues must be corrected before proceeding. Drove out, check engine light on again. Code P017B system too lean. Mechanic advised that independent auto repair shops do not have any information about P0171B. (I don't want to go to the dealer). The mechanic said that, he was going to test Oxygen sensor activity. Oxygen sensor test involves enrichment (propane, and or gas) test. O2 sensor at 1800 rpm must comply on the following: At least have seven counts per second from 0 volts, to 1 volts. For example lean (air) means down to 0 volts, and rich (gas) means to the maximum, but no more than 1 volt. The mechanic explain and show me with machine on hand. My sensor was defective, even by inducing gas (enrichment test). Replace Primary 02 sensor. Drove away, light "ON" after 40 miles drive. Back to shop pO171, the mechanic says, "Lets clean Mass Air flow meter." Meter clean, drove away, after 5 days, emmision test vehicle passed. CLEAN AIR FLOW SENSOR FIRST, to retest. Thank you, I'm a regular Owner of 2001 Sonata 4cy.