etan

the check engine light came on today. took it down to autozone to read the code. P0133 first o2 sensor. they didn't reset it or anything, neither did I. about 5 miles and half a day later the thing turned off. I believe it was while at a red light too, not too sure though i can't remember.

Is this possible? I thought that once the comp. throws a code and the CEL light came one it will stay on until it is reset. tommorow I will go down again and see if it's still throwing codes and its just the CEL isn't showing up on display.

Also, is it possible to clean an o2 sensor like how you would clean a MAF? or once they go bad there's no turning back kinda thing. times are hard and I don't want to have to spend 100+ dollars for the part if not necessary. Is there any brand in particular o2 sensor that performs well.

thanks in advance.

DeathCougar

iTrader: (23)

Those are called soft codes. They stay on for a while, and turn off. My 87 does the same thing, for the o2 sensor.

Motayota

Don't quote me on this but from what I've heard that when the non-blinking CEL comes one its because the sensor failed out of specs after 3 driving cycles. It keeps checking and if its within specs after 3 driving cycles it clears the code. I think it checks the sensor after the vehicle has warmed up to proper operating temps or something like that.

One of my pesky codes that kept appearing disappeared after I went back to a regular air filter.

etan

thanks for shedding some light on the situation.

can anybody else confirm this?

SPL15

Yup after 3 normal engine starts with no additional code errors it will turn the CEL off. This is pretty much all OBDII engines.

But it did trip for a reason. In my experience, o2 sensor codes are often caused by something other than the O2 sensor though. Usually something screwy with the ignition or fuel flow. The o2 sensor may be bad too, but often the lean or rich condition is a result of a miss or leaky injector. Unburned gas flowing through the exhaust will cause a lean condition because without a fire, the oxygen reading will be high and the O2 sensor will tell the ECM the engine is running lean, thus dumping MORE fuel into the cylinder to try & get the 14:1 ratio back. When this condition is severe enough and the ECM can't correct it by dumping more fuel, it will throw a O2 Sensor code because it will assume that the O2 sensor is bad when it cant correct the situation. It can be anything from water in the gas to leaky injector to leaky plug wires or bad plug or Coil Pack. And sadly, if enough unburned fuel hits the O2 sensor it will usually damage it as well.

arjan

I've had that happen also, long time ago. Hasn't happened again in 2+ yrs.