Service Engine Light

xmach1x · February 23rd, 2011, 05:25 PM

Hey guys I own a 2003 Mach 1 with just over 8,000 original miles. My service engine light came on and I went and got the code for the car but cannot seem to find the problem. The code is: P0420. I recently got rid of the stock Hpipe and got a Xpipe, so I was wondering if anyone has gotten this code before and how did you fix it? Thanks alot!

Calogero6685 · February 23rd, 2011, 07:37 PM

8,000 original miles!? I hate you...

Maybe your O2 sensors.

Calogero6685 · February 23rd, 2011, 07:37 PM

8,000 original miles!? I hate you...

Maybe your O2 sensors.

AndeUSMC · February 23rd, 2011, 08:05 PM

Any cats? If not, sounds like that's it.

DickH · February 23rd, 2011, 09:13 PM

get a handheld and turn off the rear o2s and the problem will likely go away if it just sarted after changing your mid pipe.

xmach1x · February 24th, 2011, 12:28 AM

Yes it is a catted Xpipe and the code came on before so I switched out the Hpipe and put the Xpipe and the code still remains.

WickedSnake00 · February 24th, 2011, 10:53 AM

I believe P0420 is catalyst below efficiency threshold. I know its an O2 sensor related code, but not 100% sure thats it. You should be able to look it up.

If you do have cats check for exhaust leaks, between the upstream and downstream O2 sensors, as well as check your O2 sensors. You can check them with a blowtorch and DVM if you'd like.

But easiest route is to just run MIL eliminators, or if you have a tuner turn them off. Problem solved.

If you want to know how to check your O2 sensors with a torch let me know and I'll post it up.

xmach1x · February 24th, 2011, 05:26 PM

I think I may have an exhaust leak because there is a puttering sound when at idle. How can I detect where the noise originates?

Calogero6685 · February 24th, 2011, 08:20 PM

Put it in the garage and shut the door, turn engine on and leave on. If you start getting sleepy, you have an exhaust leak.

But seriously, don't do that... I don't need the police showing up for assisted suicide...

Well, obviously since you have new mids, if they weren't welded and just slipped on that would be the first place to look.

xmach1x · February 24th, 2011, 10:25 PM

Thanks guys for the help I'll have to check it out tomorrow or this weekend. Just one more question, will there be some sort of evidence where the leak is exactly coming from?

WickedSnake00 · February 25th, 2011, 09:28 AM

Large carbon deposits are usually a give away, but it may not have them if it's fairly new. Otherwise you'll have to rely on hearing/feeling the leak out.

mustang3194 · February 26th, 2011, 12:41 PM

Its your 02 sensors, had the same code. get some MIL eliminators or a tune

dudelinger · March 1st, 2011, 05:19 PM

Catalyst efficiecny code, im assuming you dont have cats, or the ones you put on arent cutting it. you need the eliminators like he said^^^^

February 23rd, 2011, 05:25 PM	#1
xmach1x Newbie 2003 Mustang Mach 1 14.60@95.72 Join Date: Feb 2011 Location: Las Vegas Posts: 13 iTrader: 0 reviews	Service Engine Light Hey guys I own a 2003 Mach 1 with just over 8,000 original miles. My service engine light came on and I went and got the code for the car but cannot seem to find the problem. The code is: P0420. I recently got rid of the stock Hpipe and got a Xpipe, so I was wondering if anyone has gotten this code before and how did you fix it? Thanks alot!

February 23rd, 2011, 09:13 PM	#5
DickH MM Fanatic 2003 gt 5.4 32v on the way Join Date: May 2007 Location: Omaha Posts: 4,188 iTrader: 2 reviews	get a handheld and turn off the rear o2s and the problem will likely go away if it just sarted after changing your mid pipe. __________________ 2003 Mustang gt - usual mods - slowly working on 5.4 swap 2004 srt4 - Stock DD/winter beater Click here for your tuning needs Before asking a gearing related question click THIS link and enjoy all your saved time.

February 24th, 2011, 10:53 AM	#7
WickedSnake00 MM's king of Neon's 404 - car not found 17.81@87 Join Date: Aug 2010 Location: Diesel Engine Capital of the World, Columbus, IN Posts: 7,373 iTrader: 0 reviews	I believe P0420 is catalyst below efficiency threshold. I know its an O2 sensor related code, but not 100% sure thats it. You should be able to look it up. If you do have cats check for exhaust leaks, between the upstream and downstream O2 sensors, as well as check your O2 sensors. You can check them with a blowtorch and DVM if you'd like. But easiest route is to just run MIL eliminators, or if you have a tuner turn them off. Problem solved. If you want to know how to check your O2 sensors with a torch let me know and I'll post it up. __________________ Official Secondhand Snake Build Thread Here Looks Like a Cobra, Sounds Like a Cobra, Tastes Like a Cobra, Not a Cobra. For Sale: P71 Interceptor motor

February 25th, 2011, 09:28 AM	#11
WickedSnake00 MM's king of Neon's 404 - car not found 17.81@87 Join Date: Aug 2010 Location: Diesel Engine Capital of the World, Columbus, IN Posts: 7,373 iTrader: 0 reviews	Large carbon deposits are usually a give away, but it may not have them if it's fairly new. Otherwise you'll have to rely on hearing/feeling the leak out. __________________ Official Secondhand Snake Build Thread Here Looks Like a Cobra, Sounds Like a Cobra, Tastes Like a Cobra, Not a Cobra. For Sale: P71 Interceptor motor

February 26th, 2011, 12:41 PM	#12
mustang3194 Regular 1996 Mustang Cobra Join Date: Sep 2009 Location: Dubuque, IA Posts: 113 Blog Entries: 1 iTrader: 0 reviews	Its your 02 sensors, had the same code. get some MIL eliminators or a tune __________________ 95 Mustang swapped to a 96 Cobra Drivetrain

February 23rd, 2011, 07:37 PM	#2
Calogero6685 Because Racecar 2012 Mustang GT Premium Join Date: Dec 2010 Location: Tampa, Florida Posts: 2,037 iTrader: 0 reviews	8,000 original miles!? I hate you... Maybe your O2 sensors.

February 23rd, 2011, 08:05 PM	#4
AndeUSMC Regular 1999 SVT Cobra Join Date: Jul 2010 Location: Jacksonville, NC Posts: 58 iTrader: 0 reviews	Any cats? If not, sounds like that's it.

February 24th, 2011, 12:28 AM	#6
xmach1x Newbie 2003 Mustang Mach 1 14.60@95.72 Join Date: Feb 2011 Location: Las Vegas Posts: 13 iTrader: 0 reviews	Yes it is a catted Xpipe and the code came on before so I switched out the Hpipe and put the Xpipe and the code still remains.

February 24th, 2011, 05:26 PM	#8
xmach1x Newbie 2003 Mustang Mach 1 14.60@95.72 Join Date: Feb 2011 Location: Las Vegas Posts: 13 iTrader: 0 reviews	I think I may have an exhaust leak because there is a puttering sound when at idle. How can I detect where the noise originates?

February 24th, 2011, 08:20 PM	#9
Calogero6685 Because Racecar 2012 Mustang GT Premium Join Date: Dec 2010 Location: Tampa, Florida Posts: 2,037 iTrader: 0 reviews	Put it in the garage and shut the door, turn engine on and leave on. If you start getting sleepy, you have an exhaust leak. But seriously, don't do that... I don't need the police showing up for assisted suicide... Well, obviously since you have new mids, if they weren't welded and just slipped on that would be the first place to look.

February 24th, 2011, 10:25 PM	#10
xmach1x Newbie 2003 Mustang Mach 1 14.60@95.72 Join Date: Feb 2011 Location: Las Vegas Posts: 13 iTrader: 0 reviews	Thanks guys for the help I'll have to check it out tomorrow or this weekend. Just one more question, will there be some sort of evidence where the leak is exactly coming from?

March 1st, 2011, 05:19 PM	#13
dudelinger Newbie 1997 Mustang Cobra SVT soon! Join Date: Feb 2009 Location: Oroville,CA Posts: 48 iTrader: 0 reviews	Catalyst efficiecny code, im assuming you dont have cats, or the ones you put on arent cutting it. you need the eliminators like he said^^^^ __________________ 8:1 HCI built motor, D1SC Procharged/intercooled,custom ground cams,HCI intake manifold,MSD dig ignition,KOOKs Full Lengths,MM full tubular,Pro-motion tko 600, 3" Bassani xpipe,Magnaflows,much more! 625RWHP/510RWT

Remove Advertisements Sponsored Links
Ford Mustang Forum Advertisement

Threads Similar to: Service Engine Light
Thread	Thread Starter	Forum	Replies	Last Post
Battery Light/Service engine soon light	Genevieve!	99-04	21	March 12th, 2011 10:51 AM
Service Engine light	Squints	All Other Vehicles	3	March 5th, 2010 03:41 PM
Service Engine Light	PowerShiftz02GT	99-04	13	May 20th, 2008 09:28 PM
Service Engine Soon Light?	joka187	V6 Mustangs	7	December 13th, 2007 01:02 PM
Service Engine Light	Vettefast	2005 - 2010	7	November 27th, 2007 10:48 AM

All times are GMT -4. The time now is 04:57 PM.
Contact Us - Modded Mustangs : Ford Mustang Forums - Privacy Statement - Top
Modded Mustangs is ©2005-2008, All Rights Reserved, And is Not Affiliated with Ford Motor Company. Forum is powered by vBulletin ©2000 - 2012, Jelsoft Ent. Ltd. & SEO by vBSEO 3.3.2 ©2009, Crawlability, Inc.