scottyrabb

I have a 1999 Lexus ES 300 with 60k miles on it. A few days ago, I took my car to a mechanic to fix a valve cover gasket leak. They did the job, but when I got the car back, the Check Engine and Trac Off light were both on. I immediately brought it back and they said some wiring on the front oxygen sensors were loose because they were bad to begin with. They also said it was no big deal and I could continue driving with it, but the lights might flicker on if the road was bumpy. I haven't noticed much of a difference in performance/mileage, but the lights have stayed on the whole time.

1. Did the mechanic break the O2 sensors with the valve cover gasket job? The CEL/ Trac off lights were not on when I brought the car in. If he did, should I ask him to replace my O2 sensors for free or pay for the part myself and ask him to cover the labor?
2. If I don't fix it and don't notice any obvious mileage changes or smells etc...what will be the long term damage? Is this something that can wait a few months?

Thanks all for your help!

DGIKULJOT

The wiring harness has to be moved out of the way and wrestled when doing the valve cover job. I doubt the oxygen sensor it self is broken. More than likely either the oxygen sensor isn't plugged in or they broke one of the wires in the harness. You should find the oxygen sensor and follow the wires into the harness and see if there are any obvious signs of a broken wire. if you can't find anything, Defiantly have them fix it and tell them you think they broke a wire. You can continue driving it like that but in most states it won't pass emmisions testing like that. Also if someone else has to fix it and they want to replace the whole harness it can get expensive so have them take a look while you have a chance.

1sWt2GS

iTrader: (6)

valve cover gasket and o2 sensor are nowhere near each other.

you can drive with an o2 sensor on, there would be no problems (except smog, emission related) and the car may run rich. personally I have OCD and the check engine light would just bug me.

DGIKULJOT

Oh yeh so there are 2 oxygen or air fuel ration sensors under the hood. One in front of the radiator on the exhaust and the other one is behind the engine, passenger side on the exhaust.

mitmaks

I don't see how changing valve cover gasket would affect O2 sensor. They might've forgot to plug in a harness.
I would check code to see which code(s) you get, maybe its not even O2 related.

scottyrabb

mitmaks after I brought it back in with the warning lights on he confirmed it was the O2 sensors. The lights were not on before the job, and now they are on. What else could explain this if he didn't do something to the O2 sensors?

mitmaks

Did he tell you which codes is it giving you? If it wasn't on before he should fix it so it's not on. If he broke wiring somehow, he needs to fix it.

scottyrabb

No he did not tell me the actual codes, just that some of the wiring was bad to begin with. He reset the lights so they were off at the time but they came back on about a mile later. So in your opinion it is possible that he broke the wiring doing the gasket job? I told him to fix it for me but he claims they were faulty to begin with. He also said it was okay to drive around with but I might notice a change in mileage. What should I do? Thanks again.

mitmaks

He told you it will be fine to drive it like that? Sounds like some shoddy mechanic to me, where did you find this guy at? Definitely have it fixed. You don't want to loose mpg due to o2 sensor not being plugged in/bad wiring. And of course you won't pass emissions with CEL on.

PFB

You could end-up ruining the Catalytic converter, so it needs to be dealt with.

It could have also been a freak coincidence who knows, however at your current 60k miles, they should still be good.

Phil

DGIKULJOT

You guys know when the VC gaskets are changed you really have to man handle the wiring harness to get it out of the way especially if you dont see some of the hidden screws

Pretty good chance they broke the wiring during this step.

davensd

I agree. A bad O2 sensor is a quick way to burn through your cat. Find a real mechanic to get the issue resolved, it will be better for the car in the long run.

Davensd