o2 sensors

Just wanted to know if O2 sensors or cats are bad would they throw a code to the OBDII for a 99 F150 with a 5.4. How would you tell that they are bad if there is no code and can they be cleaned. I was told you could clean the MAF sensor with gumout. Could you do the same with the O2 sensors? Thanks Again

I have heard that you can clean O2 sensors with a wire brush.

both 02 sensors will show a code. the down steam 02 monitors the cat, if the cat was clogged it would show a code for that. you can check them with a dmm it will show about 100mv or less with engine off

First of all, your o2 sensors act like thermalcouples. They have a metal coating over them that when there is a temperature difference they create a voltage potential. The computer reads this potential, and decides how the system is operating. so, if you use a wire brush to clean them off, you will remove the outer coating and render them useless. If you want to clean them use something like elecktra contact cleaner, the same for your maf. Oil based cleaners may inhibit the readings, or damage the sensor(s).

First of all, your o2 sensors act like thermalcouples. They have a metal coating over them that when there is a temperature difference they create a voltage potential. The computer reads this potential, and decides how the system is operating. so, if you use a wire brush to clean them off, you will remove the outer coating and render them useless. If you want to clean them use something like elecktra contact cleaner, the same for your maf. Oil based cleaners may inhibit the readings, or damage the sensor(s).

Thanks guys, I got a Fluke 79 3 for work which will read deep enough resistance to get the info I need. Kind of what I thought though. I have no codes, but a killer running engine but gas mileage has dropped significantly since new and a tune up with new plugs so I wasn't sure if this was the problem. I used factory plugs with same part number.