2002 grand prix 3.1 ses light on code po420
BIGPETEG24
09-27-2010, 04:21 PM
ses light went on , i put the scanner on it and got a error code PO420 cataltst system below threshold bank 1. where do i start to find the problem ? any pointers would be much appreciated.
tblake
09-28-2010, 12:49 AM
How many miles?
Start by checking for exhaust leaks before the cat converter.
Start by checking for exhaust leaks before the cat converter.
BIGPETEG24
09-28-2010, 05:23 PM
130,000 miles
tblake
09-28-2010, 09:09 PM
GM extended to warrenty on cat converters on 01-02 grand prix's with the 3800 motor due to known issues. The warrenty was extended to 120k miles, so you just missed the mark, but you have the 3100 motor, so the warrenty is probably a moot issue anyways.
http://www.automotiveforums.com/vbulletin/showthread.php?t=681283
If you don't have any exhaust leaks, you may want to consider purchasing a new converter and having an exhaust shop weld it in. You could get an aftermarket converter on a site like ZZP for roughly 60.00, and the exhaust shop near my home charges 40-50.00 to cut the old one out and weld the new one in.
http://www.automotiveforums.com/vbulletin/showthread.php?t=681283
If you don't have any exhaust leaks, you may want to consider purchasing a new converter and having an exhaust shop weld it in. You could get an aftermarket converter on a site like ZZP for roughly 60.00, and the exhaust shop near my home charges 40-50.00 to cut the old one out and weld the new one in.
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