I am looking at a 2002 mazda 626 with 69,000 miles to purchase for a commuter vehicle. The check engine light is on and I am told that it is just an 02 sensor nothing to worry about. What is an 02 sensor and what should I do to properly maintain the car?
Hopefully i can help..
The o2 sensor /lambda sensor / Oxygen Sensor as they are known by detects the amount of oxygen in the exhaust gas and sends a signal to the engine control unit which in turn adjusts the air & fuel mixture to its optimal level.
Too much oxygen in the exhaust gas indicates a lean mixture, which can cause performance problems, including misfires etc. Too little oxygen indicates a rich mixture, which essentially wastes fuel and results in excess exhaust emissions which can result in an emission test failure and can harm the catalytic converter caused by excess fuel - so i wouldn't say it would be something to ignore or not worry about.If the o2 sensor has been diagnosed as faulty then it would be well worth having that replaced if you do decide to purchase the vehicle it will be located on the exhaust system and should be easily replaced once you acquire the sensor again should be easily available from any local motor factors or dealer even..another thing to check up on is the timing belt / service history and ensure that has been replaced upto now at that mileage or before hand if not then you may looking at having that replaced so that would need to be inspected..properly maintaining would obviously inc regular,or yearly servicing ie: regular oil/filter changes / spark plugs/fuel filters /air filter / antifreeze checked /brake fluid checked etc.obviously this wouldn't inc general wear and tear items such as brake pads/clutch/tyres/suspension wear etc which should also to be part of a check list when servicing..so as above it would be advisable to have the o2 sensor replaced rather than ignore it..as the engine light will continually be coming on until such time the fault is cured and then the light shouldn't come back on once the codes have been cleared..
Fully trained 19+yrs exp/self employed technician in the UK
Thanks so much for the reply. Should I ask them to replace the sensor? If the sensor isn't faulty then there are other problems with the car. How do I determine the best fix? They are asking $6000 for the car what should I do?
If its dealer then it should be a fairly straight forward replacement for them and i don't see why they wouldn't replace it if they are wanting a sale, so i would definitely ask about having this done before you actually agree to buy it - once its fixed and the check engine light is out then you can make a decision to purchase it - though sometimes these can get a little seized up on the exhaust which inst really uncommon so they might need to heat it up a little to free it up - so again i would maybe try and insist they replace it - if they aren't willing to do that then id be a little cautious as the problem in regards XX XXXXXX light "could" relate to something else entirely maybe more expensive they not telling you about - Without knowing what the ecu is seeing as faulty ie: "fault code" then its basically taking their word for it that the o2 sensor is at fualt and just needs replaced - if possible and whether the sellers agree or not is to maybe have mechanic or local garage you know off maybe do a check over on it a bit like a detailed pre-inspection before you buy and see if they can find out what the fualt code is?..so as above maybe have a word with the seller/dealer which ever and see if they are willing to sort that problem out for you as above..