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Oxygen sensor 99 Ford Contour SE

Hi All,

Need some advice. My check engine light came on and code revealed PO174 (System too lean Bank 2)on my v6, 75,000 mi 99 Contour SE. My mechanic said it was an oxygen sensor in need of replacement. He cleared the code and advised if the check engine light came on again I should schedule the replacement of the oxygen sensor. How many oxygen sensors are there? Does the above code narrow it down to the exact one? Does it make better sense to replace all of the sensors at once? Any idea how much the parts cost. Is it safe to be driving around with a qustionable O2 sensor? All advice greatly appreciated. Thank you. Ban

Did your mechanic measure the signals coming from the oxygen sensors? If not, find one who will do actual troubleshooting. The computer codes don’t point directly to what part or parts to replace. You could have a leaky intake manifold gasket or a faulty fuel injector.

Your mechanic is saying, by blaming the oxygen sensor that it is doing its job wrong…which is to detect lean, or rich, conditions. It must be mechanical ESP! The same thing could be determined by reading tea leaves.
You need a mechanic who will check the operation of the oxygen sensors, and check for vacuum leaks and/or sources of unmetered air. The lean condition (air/fuel mixture) could be caused by inadequate fuel flow (injected fuel), also.

Thanks Circuitsmith,
I’m new to the board and you guys are awesome. I’ll be using your advice with my new mechanic. Are there any 99 ford contour se books “for dummies” or ladies with zero mechanical education who panic at the garage? Best, Ban

Thanks Hellokit,
I will keep the above in mind and discuss with my mechanic. I’m trying to get more educated on this stuff. I generally am an ill-informed consumer and probably get taken to the cleaners more than I know. Best, Ban

This site has some good information on sensors and how to check them. (Click on said site, to open.) And, this site:

Great stuff. My head is spinning. Thank you. Ban