If a 1997 Mazda 626 engine light keeps coming on and the mechanic already changed the oxygen sensor what else could be causing this to happen?

Hi guys ( and gals)... had the same problem on a UK registered 2001 626 GSi Automatic ( not Ford Built ) at about 100k miles and took it to my main dealer with a virtually full tank of petrol ( see below) for a computer code check as the problem was intermittent..they diagnosed and fitted a new lambda sensor ( at great cost ) which seemed to cure the problem until fuel ran low...got the warning light back!.

Noticed that when I had refueled, it was fine but when fuel was low, the light came on and the car started missing a bit..It felt almost like fuel starvation like on old motorbikes that I owned years ago but filter was clean / almost new. Will add that car was serviced "almost religiously"!!

Went to a backstreet garage nearby who diagnosed at once "fuel pump failure"...the weight of the fuel was forcing it through the system and as fuel was used, less was getting to engine, getting leaner etc, etc! Fitted ( cheaply ) pattern fuel pump, problem solved, gave the car away in 2007 with 250k miles on clock when I bought my latest Mazda 6 and it is still going strong locally!

My advice is, check fuel pump before lambda O2 sensor...it's easy now I know, pull the pipe off the connection block and see the flow, if you get soaked in petrol, the pump is ok ( and don't go near a naked flame!), if not, likely to be pump

Following answers are nothing to do with me but where I have probably tapped into the wrong section and posted incorrectly... please observe and respect their solutions..who knows, they are probably right and little me, in Cornwall, UK is wrong! Have the proverbial, " Nice Day "

There's no way to know until you hook up an OBD-II code scanner to read the codes. There are several scanners available on the market, the cheapest is around $122 but any decent garage should have one these days. The Mazda uses ISO 9141-2 protocol.

There's a nice list of OBD-II codes here http:/autorepair.about.com/cs/troubleshooting/l/bl_obd_main.htm

i had the same problem.. i found a wire pulled out of the pin at the connector, not to far from the o2 sencer..

error code 0171. system to lean. today just changed fuel filter, Mazda 626 97. not sure if the error code will come back or not. will know tomorrow,

Funny, I dealt with this today, mine came on and i hooked it up to the ODBII and it read "system to lean" im assuming the fuel filter needs to be changed.

I have a 1999 Mazda 626 with a 4 cylinder that needed the intake manifold gasket replaced. I was told it was a common problem for the gasket to leak. The leak at the gasket will cause the car to run lean because of increased air. My car also had an idle problem.

I had the same problem with my 1997 626 it come to find out i had an exhust leak and i also had a trans problem. The exhaust leak made my car run real lean.But ya your best bet is to hook it up to the ODBII to get the code or codes and go from there.

If the CE light comes on, drive to your nearest Auto Zone store and they will check it and give you the codes for free.

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I had a code coming back "system too lean" also a code that the O2 sensor had a problem and "catalytic converter not efficient. The engine acted like it was running out of gas and the tranny even gave me trouble and had a code on that too. Another code said I may have a dirty MAFS. They make a MAFS cleaner to spay on and clean. All the codes went away and the problems were fixed for $7 !!! Makes sense if the engine is not getting the right air combination to start with all the other sensors will pick up a bad reading. By the way...an auto repair shop charged me $100 to diagnose this and give me the codes and concluded I needed a new cat converter at $1300 , a rebuilt tranny at $2,800 and clean the MAFS at $60

Autozone gave me the same codes for free.