Cel p0140

tweakingmsp

Member
:
2003.5 MazdaSPEED Protege
As the title says, CEL P0140. I know that its O2 sensor ckt no activity (bank 1 sensor 2), but thats all the more I know. Can someone please explain what CKT and bank 1 sensor 2 is?
 
Not sure about the Vibrant layout but if it's catless and you do not have a non-fouler or MIL eliminating wire set up then you will get that CEL. If you do have either one and have it then you can try to clean the O2 and see if that goes away.

I get that CEL every so often and it goes off on its on. I quit cleaning the O2. Until mine is truely dead I am not replacing it as it's basically meaningless since I have no cats.

PS its the 2nd O2 downstream and yours is telling you that no activity was detected in the circuit. Weak signal to the pcm for some reason.
 
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I do have a high flow cat. I thought it was the O2 sensor furthest back. I was thinking since I have the Vibrant, I had to extend the O2 sensor wires. Maybe the wires just came undone.
 
It is the last one in the exhaust chain. 1st one is in your exhaust manifold and that is the one that is the most important.

Check your connection and take it out and clean it, it may just be carbon fouled and not really dead.
 
It is the last one in the exhaust chain. 1st one is in your exhaust manifold and that is the one that is the most important.

Check your connection and take it out and clean it, it may just be carbon fouled and not really dead.

Is there a certain way to clean the O2 sensors?
 
I always used CRC Electronics cleaner. You could also use brake cleaner. Just take it out with 7/8 wrench or Sensor socket after disconnecting it from behind the intake manifold and on the little bracket on the rack mount. Spray it a few times and let it dry and put it back in.
 
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When I get time, I'll have to crawl underneath and check. If it is dead, how much does one cost?
 
You should be able to get a direct fit for less than $120 either rockauto.com or oem.

In 78K I've cleaned mine 4 times. After the 4th time the CEL did not go out right away but did eventually. Now it just comes up randomly but goes away on its on.
 
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