Could still need a O2 sensor, but if it's too lean the O2 will not produce
any activity... thus the fault. He needs to fix the lean/rich faults first.


"Brian Running" > wrote in message
news
>> Looking for opinions, I have an issue where the check engine light is
>> coming on. I recently gave the car a tuneup which cleared the misfire
>> codes it had, but now (1 week later), I have the following codes
>> present:
>>
>> P1128 Long Term fuel trim too lean
>> P0172 System Too Rich
>> P0134 Oxygen Sensor Circuit - no activity detected (pre-converter
>> sensor)
>>
>> I am guessing that the O2 sensor needs to be replaced, but will this
>> also fix the other codes? I haven't detected any vacuum leaks that
>> might be suspect. Any help would be appreciated. Thanks.
>
> I'm not like a lot of the guys here -- just dumber, probably -- but I tend
> to go with hunches, if they're supported by any evidence. In your case, a
> dead O2 sensor would affect fuel mixture, so that would say to me, "Go
> ahead and replace the O2 sensor and see what happens." Odds are, it will
> fix the problem. If not, you can at least tell yourself it was not a
> total shot in the dark, it was a supportable decision, and what the hell,
> it looks like you needed a new sensor anyway.
>
> I went ahead and replaced a mass-airflow sensor recently, due to a
> fuel-mixture code. They have a reputation for failing, so I rolled the
> bones. Sure enough, it did the trick. There's still room for
> seat-of-the-pants mechanics in this computerized age.