2003 Mach 1 Catalyic Converter Code

xmach1x · Oct 17, 2010

Hey guys this is my first post I just purchased a 2003 Mach 1 and have a question about it. When I start up the car white smoke shoots out of the exhaust of the driver's side. The engine light came on and I got a code for it, P0420. The explanation: The oxygen sensors monitor the Catalyic Converters ability to store oxygen. Has anyone ever gotten this code and what did you do to fix it? Thanks.

trombonedemon · Oct 17, 2010

Excessive EGR flow Escape-Your EGR valve might be stuck open, you can always clean or replace the valve, pretty simple for the home mechanic.

trinity_gt · Oct 17, 2010

xmach1x said:
Hey guys this is my first post I just purchased a 2003 Mach 1 and have a question about it. When I start up the car white smoke shoots out of the exhaust of the driver's side. The engine light came on and I got a code for it, P0420. The explanation: The oxygen sensors monitor the Catalyic Converters ability to store oxygen. Has anyone ever gotten this code and what did you do to fix it? Thanks.

P0420 is a cat efficiency code. The car came from the factory with 4 oxygen sensors, 2 in front of the cats (used for fuel control) and two behind the cats (used to determine if the cats are working). This code means that the PCM thinks the signal from the passenger-side (bank 1) rear sensor is showing that the cats on that side are not working.

Given that you just bought it, are you sure the previous owner didn't install an O/R (off-road) midpipe?

xmach1x · Oct 18, 2010

No the car is completely stock. It hasnt even reached 5000 miles on the odometer yet. A buddy of mine thinks maybe the code came on because it sat in the previous owners garage without it being driven enough.

How could I go about cleaning it out?

trinity_gt · Oct 19, 2010

xmach1x said:
No the car is completely stock. It hasnt even reached 5000 miles on the odometer yet. A buddy of mine thinks maybe the code came on because it sat in the previous owners garage without it being driven enough.

How could I go about cleaning it out?

The car is 7 years old and has less than 5000 miles on it? Wow.

Clearly it's spent a good deal of time in storage. It's possible the 2 sensor(s) have degraded due to condensates and the like damaging the sensing element and may simply need replacement.

You might try clearing the code and taking it for a decent highway run to see if the code returns. If it does then you're probably looking at a replacement sensor.

xmach1x · Oct 19, 2010

Yeah it was great find. The guy I bought it from had it stored in his garage. If I do some highway runs will the light go off or do I need to clear it first? Do you think both sensors on bank 1 would need to be replaced?

trinity_gt · Oct 19, 2010

xmach1x said:
Yeah it was great find. The guy I bought it from had it stored in his garage. If I do some highway runs will the light go off or do I need to clear it first? Do you think both sensors on bank 1 would need to be replaced?

If the condition goes away the light will go off but the code will remain. Keep in mind that a MIL due to a (perceived) cat efficiency problem will not affect performance.

I wouldn't replace anything that the computer isn't indicating. If the computer is happy with B1S1 I'd just leave it be.

xmach1x · Oct 19, 2010

Yeah I havent had any driving or performance problems, and thats what the code said. Its more that it just annoys me when Im driving.

2003 Mach 1 Catalyic Converter Code

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