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rpmdiag, Tech and Instructor
Category: Subaru
Satisfied Customers: 8132
Experience:  Since 1975
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Car starts fine came in with code 02 sensor-replaced--on

Customer Question

car starts fine came in with code for rear 02 sensor-replaced--on initial start the fuel trim numbers are present but in a bit they go to 0---i can unplug both 02 sensors and it will not set a code. no codes are present- replaced ech wit a known good unit-still same--
Submitted: 1 year ago.
Category: Subaru
Expert:  rpmdiag replied 1 year ago.

Hi, I’m Ron and I can help you.
I have been in this business since 1975 and also teach automotive repair. I am confident we can resolve your problem together. Please understand that I don't know your skill level. I can't see, smell, hear, or touch the vehicle either, so it may take a few replies to get to satisfactory results. Please be patient!
I also try to give all of the information you may need, expecting a “positive rating” in return. I will also continue assisting you after you have rated me, if necessary. If there is any reason I cannot get a positive rating, please let me know why “in advance”, so I can go another direction for you. I am sorry you’re having this problem; I’ll help you through it.

Ok, when codes set, it doesn't mean replace a part all the time. There can be other factors involved such as wiring issues or bad computers, including swapping with a "known good one". A scan needs to be done checking at idle and load and wot, to see what happens to STFT AND LTFT. I would also clear the codes and start over at this point.

Thanks, Ron