2003 Pontiac Sunfire Check engine light/ catalytic converter?

JRAPP61

MEMBER
2003 PONTIAC SUNFIRE
136,000 MILES

I have had the check engine light on for some time now, autozone says it is the catalytic converter?/ Emmission problem? How longail do I have to have it fixed and what does it cause? My car does not stall or anythong will this keep from getting inspected and this really serious to my engine or exhaust. I had this happen before but the mechanic said it was my front emission something and fixed does this mean I have a front and back part of my converter? I do not understand Please explain! Thank you!

1 Reply

FREEMBA

MECHANIC
1,152 POSTS

Ok, here goes. The catalytic converters' purpose is to convert many of your cars pollutants in the exhaust system to carbon dioxide and water before they exit the tail pipe.
Before the exhaust reaches the converter it is monitored/read by an oxygen sensor [up stream or #1 oxygen sensor] and this info is sent to the computer. The exhaust is monitored/read a second time [by the downstream or #2 oxygen sensor] as it exits the converter and this info is also sent to the computer.
The computer compares the first reading to the second reading and determines if the catalytic converter is indeed doing its job. The first reading of the "untreated "exhaust should be higher than the second reading after the exhaust has been "treated" by the catalytic converter.
If both oxygen sensor readings are close to being the same, the computer "believes" that the catalytic converter isn't working properly and turns on the "Check Engine" light.
However the code alone does not mean that the catalytic converter needs to be replaced. There is a process which you have to go through to be sure. Mainly because a faulty oxygen sensor could convince the computer that the conveter is bad, causing you to replace the converter [and not the faulty oxygen sensor], and yet having the problem remain.

Please post the codes number that you got when you have the computer scanned. Thanks.