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O2 sensor error

T

tuononero

New member
Hi guys.
since I bought my grand prix I keep having my engine light on related to the o2 sensors.
I replaced both the upstream and downstream sensors and I have also erased the errors with the tech 2 plus u checked the values of the sensors with the tech 2. They pretty much seem to match. The check engine light keeps coming up tho.

On my exhaust, after the cat (un the middle section) I got rid of the silencer and I put a straight pipe. Could it be the reason why it keeps giving me the error? Could it be a faulty pcm? Or maybe I need a new cat?

I understand I'm not giving so many useful info but I'm hoping in a common problem.

Thanks
 


The codes don't really mean that the sensor is bad and should normally always read correctly with a scanner and show no signs of bad mpg or sluggish performance.

They are just saying that the computer is not seeing the correct amount of switches lean and rich of stoich (450-550mv) in a given amount of time. Say it needs to see 90 switches in the 60 second test but only saw 80, it then sets the code are 2 failed times. It's a pretty common problem with header installs because the o2 sensor placement is now different but I haven't seen much of this problem on stock exhaust.

I only use AC delco/denso sensors too, I feel that bosch sensor end up giving people problems.
 
Yes and no but mainly no.

The sensor itself is working just fine but just in the first test the car does for the o2 sensors (it only does the test once per drive cycle I believe) it didn't switch enough times. It's possible the new sensor isn't working correctly at that given point. If you can warranty the sensor, do so and see what happens.
 


I have no warranty for the sensor, and btw same thing happens for the downstream sensor.... i don't remember the code now.
So this is my question, before buying another pair of sensors what other problems can cause this result?
I thought of a leak in the exhaust leak, but i'm not sure. What else?
 
A poor electrical connection or a long shot being that you have a small vacuum leak going on.

The scanner would be able to show you the fuel trims, anything positive or above 6-10% all the time if a possible vacuum leak. Bad leaks will show +16.4 all the time.
 
being you have a 02 and no cat i believe, you said silencer? wrong terminology for what ever part you mean. will set the rear o2 code, as its failing the cat test and over fueling and that might be burning up your o2 sensors.

heater element's go bad, replace the sensor, use only delco sensors, no idea what brand you used but aftermarkets are not always so good and can fail or not work right.

if you have no cat you can try a simulator thing, or a pair of bungs to pull the o2 out of the pipe to trick it to read right.
 
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