The car idles rough or stalls. Sometimes runs good. The codes then showed a bad o2 sensor on bank 2 I had it replaced but the check engine light still came on with the same code. Then I replaced the fuel filter and idle air control. I just read the codes again. Here are the new codes The old one cleared itself. Now it says code PO511 Idle air control circuit. And P1633 keep alive power voltage too low. Please give me an explanation for what this means. Does it mean that the replaced idle air control is bad and that the battery is low?