1998 honda civic check engine light came on but what does the code mean? I took it by AutoZone and they told me its code is P0135 and they just gave me a ticket stub what the faults are... Showed "A/F sensor 1 heater system malfunction probable cause". Not sure what A/F stands for but it did not specify what exactly to replace.. I have been looking online and it seems to show a oxygen sensor but not sure which one? I overheard the AutoZone guy asking another person about the code and the other guy said sensor 1 means before the converter... Can anyone post any links to what the code stands for that is causing my check engine like to come in? I have tried to disconnect battery and reconnect and the check engine light came back in so if its an easy fix I would just like to get it fixed.. Please post you guys... Thanks..