Hello I have 2001 grand marquis mercury
Hello I have a 2001 grand marquis mercury
and my check engine light is on so I took it
to AutoZone and a popped up which is
P0420 indicates that the bank 1 Catalyst
system efficiency was below threshold for
a predetermined period of time can you
please help me fix the problem or any idea
of what it could be?
This is telling you that your catalytic converter is worn out and needs to be replaced. Try this, using a hand held scan tool clear the computer. See if the code resets and the check engine light returns. You must keep the gas tank between 3/4 and 1/4 for the computer to check the catalytic converter. So once you clear the computer don't fill up for a few days. If you have to add gas only put enough in to keep the tank within that range. If after about a week the code doesn't come back, you're ok. However, if the code returns you'll need a new catalytic converter. When shopping for a new catalytic converter you must know if your Grand Marquis has Federal Emissions or California Emissions. The emissions decal under the hood will tell you. Consider a universal catalytic converter. They're much cheaper and work just as well as a direct fit unit. I've had a universal converter on my 2000 Grand Prix since 2013 with no issues! HTH. -Jim
I have a 1995 Grand Marquis. Can i use a catalytic converter from a 2001 Grand Marquis
Not if you have to pass smog inspections.
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