My check eng light come on my o2 sensor was bad i put on a new 1 put the neg cable back on run fair for a few miles then it come back on running bad so i toke the neg cable off again and put back and it run again for a few miles run bad again check all my fuses

SOURCE: 96 Ford truck engine lIght will not go away.

this is the problem with code readers they bwill tell you the code and sometimes even have a reset feature. However they do not tell you the parameters and don't have an drivability feature so you can not test the ecm and all the sensors or modules while engine is running. diagnostic scan tools are very expensive and hard to use unless you have been trained to do so and PEP BOYs is not what I call real reliable mechanics to begin with. Now I concure with toddG on his reasoning in what might be the potential fault. if your vehicle is running rich or lean your O2 sensor will pick this up on the exaust side, however it is not the sole sensor responsible for the ecm adjusting the fuel air mixture.. you stated that you have switched out several o2 sensors and the fuel pressure regulator, but there is also you mass air flow sensor, your TPS sensor, as well as your map sensor these are worth checking out and just because a faulty sensor is the problem doesn't mean you will get a code each time. the system is built with redundancy in order to keep the vehicle running. in order to get the best possible diagnois take it to a shop where they have a full diagnostic scanner this will have not only OBD1 and OBD2 but cam protocol as well. while the tech is scanning the vehicle he will be able to see how the engine is performing under realtime conditions. please rate this as well as change the rating for toddg because he did offer a valid suggestion

SOURCE: Engine Fault light illuminates. Ford KA Collection

have you totally cleaned the fuse box and fuses

Marvin

• 85242 Answers
• Posted on May 01, 2009

SOURCE: all 4 o2 sensors read bad

daves944 knows what he is talking about, u need to find the root cause of this problem, which is a problem any of th following can cause this, MAF, Intake leaks, engine conditions like low compression and many other things, the O2 codes are a Symptom not the problem, you may also have a wiring harness problem, check the harness connectors to the O2 sensors, look for exhaust heat related wiring damage, look for corrosion in connectors.

SOURCE: 99 explorer running rich check engine light wont come on

coolent temp sensor to pcm . the truck thinks it cold and its riching the fuel mixture . its a cheap part . i would have a good shop with a good scaner check it fist but thats up to you

SOURCE: o2 sensor reads bad

I hope you didn't just change out 1 sensor, the car has a minimum of 2 O2 sensors, and if you have a dual exhaust system, then it will have 4 O2 sensors.