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Ron Z.
Ron Z., - Saturn Tech -
Category: Saturn
Satisfied Customers: 18966
Experience:  18+yrs experience. State Inspector and Saturn Diagnostics
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Saturn vue: check engine light..catalytic converter..clean sensors

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06 Saturn vue the check engine light on and won't go off had it checked 5 times told no code had it reset light still on now I paid Firestone $90 to check it they tell me they are getting a 02sensor and catalytic converter code. Do I go with them and opt to clean sensors (another $90) or just replace sensors and possibly catalytic converter ( big money) or should I have it tested somewhere else (not noticing any problem with car).
Welcome to! My name is DriveFast71(Ron) and I will do my best to answer all of your questions completely and accurately.

Did they happen to provide you with the "p-code" that pointed to an O2 sensor and/or converter?
Customer: replied 5 years ago.

On GM vehicles, the P0420 is a fairly straight forward code that does point to a failing catalytic converter. The oxygen sensors measure the amount of emissions going into, and then out of the converter. When they see that the converter is not "cleaning" the exhaust to meet GM specs, the converter is deemed "below threshold" and the P0420 is set. If this were to be an oxygen sensor, the appropriate p-code for the faulty sensor would also be set (ie. P0135). Make sure there are no exhaust leaks in the system. Make sure there are no current cylinder misfires. If these check out, then most commonly, with the P0420- the converter is "on its way out" and will need to be replaced. Heep in mind, the replacment converter MUST meet GM specs. Those "universal" or "discount" converters they sell at AutoZone will NOT meet GM specs, and will not solve the problem. With GM, i've had fairly good results with the brand name "Walker", which usually sell for around $400.
Ron Z. and 3 other Saturn Specialists are ready to help you
Customer: replied 5 years ago.
Ok lets say no leaks or misfires so do I replace both catalytic converter and 02 censors or just catalytic converter and why did the code not show the other 5 times tested .
You only need to replace the "main" converter (aka Three-Way Catalyitc Converter)(see image below). No need to replace the Oxygen Sensors, as they are working fine if they can detect the loss in oxygen storage capabilities of the converter. If the code did not show before, more than likely the converter is "on its way out" and not fully gone yet. It is possible for the internal make-up of the converter to clean efficiently at some points, and then not at others (more likely to show a failing when hot as opposed to when cold).