Hello I have 2001 grand marquis mercury

Asked by Oct 20, 2016 at 10:30 PM about the 2001 Mercury Grand Marquis LS

Question type: Maintenance & Repair

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?

1 Answer

66,175

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

2 of 2 people found this helpful.

Your Answer

Add photo

Related Questions

Search Mercury Grand Marquis Questions

Mercury Grand Marquis Experts

#1 Tracy Hooks
Tracy Hooks
Reputation 5,470
#2 kbro
kbro
Reputation 2,060
#3 Js08016
Js08016
Reputation 1,770
View All

Related Models For Sale

Used Ford Crown Victoria
12 Great Deals out of 1,069 listings starting at $2,995
Used Lincoln Town Car
33 Great Deals out of 1,820 listings starting at $1,750
Used Chevrolet Impala
521 Great Deals out of 31,726 listings starting at $1,450
Used Ford Mustang
474 Great Deals out of 45,735 listings starting at $1,999
Used Ford Taurus
250 Great Deals out of 20,434 listings starting at $699
Used Ford F-150
2,198 Great Deals out of 206,316 listings starting at $1,499
Used Chevrolet Tahoe
549 Great Deals out of 29,235 listings starting at $1,699
Used Cadillac DeVille
7 Great Deals out of 1,640 listings starting at $1,999
Used Chevrolet Silverado 1500
1,716 Great Deals out of 175,753 listings starting at $1,250
Used Chevrolet Camaro
226 Great Deals out of 30,943 listings starting at $1,217

Used Cars For Sale

2010 Mercury Grand Marquis LS For Sale
5 Great Deals out of 90 listings starting at $2,799
2009 Mercury Grand Marquis LS For Sale
6 Great Deals out of 85 listings starting at $3,790
2008 Mercury Grand Marquis LS For Sale
7 Great Deals out of 101 listings starting at $2,250

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.