P0421 and hesitation hyundai sonata 2003 - Hyundai Forums : Hyundai Forum
 
LinkBack Thread Tools
#1 Old 06-25-2013, 02:47 PM
Junior Member
 
Join Date: Apr 2013
Location: louisville kentucky
Drives sonata 2003 4 cyl
Posts: 20
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
goldsonata2003 is an unknown quantity at this point
(Thread Starter)
P0421 and hesitation hyundai sonata 2003

My 4 cylinder 2003 sonata has its check engine light on with the code p0421 and hesitates when I try to accelerate too fast but doesn't hesitate all time, sometimes it will and won't, I've read up that there are other things that can cause the code to read such as exhaust manifold leak, spark plugs and o2 sensors. How would I be able to check if these parts are the problem and need to be replaced before I dish out 800$ for a new catalytic converter? I recently installed an egr valve and solenoid if that could be the problem too, any help will be greatly appreciated, while at Sam swope today I got a diagnosis and the guy said it was the cat but I don't think he did any work other than read the codes since I had a coupon for a free diagnosis and tire rotation

Last edited by goldsonata2003; 06-25-2013 at 02:50 PM.
goldsonata2003 is offline  
Sponsored Links
Advertisement
 
#2 Old 06-25-2013, 04:54 PM
Senior Member
 
Nightstalker2160's Avatar
 
Join Date: Jul 2012
Location: Southeast USA
2004 Sonata, 2.7L auto 2005 Santa Fe, 2.7L auto
Posts: 153
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Nightstalker2160 is an unknown quantity at this point
What does that mean?

Basically this means that the oxygen sensor downstream of the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
Symptoms

You will likely not notice any drivability problems, although there may be symptoms. The code may be more likely to occur after the engine has had numerous cold starts in the past 1-2 days.
Causes


A code P0421 may mean that one or more of the following has happened:
  • The catalytic converter is no longer functioning properly
  • An oxygen sensor is not reading (functioning) properly
  • A sparkplug is fouled up
Possible Solutions

Measure the voltage at the oxygen sensor on Bank 1 (the rear sensor, or the sensor after the converter). In fact, it would be a good idea to test each oxygen O2 sensor while you're at it.
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.


++++++++++

Above is what I came across. I would start with checking the O2 sensors (there are two). It's the cheapest. If it's been a while since the plugs were changed I'd give them a look also.


EDIT+++++

More info straight from the Hyundai service site.

P0421
Main Catalyst Efficiency Deterioration (Bank 1)
a.Catalytic converter deteriorated
If any codes relating to HO2S sensor. MAFS, injectors, a P0171 or a P0172 are present, do all repairs associated with them before proceeding with this trouble area.


P0171
Fuel System Too Lean (Bank 1)
a.Faulty ignition system (Ignition coil/spark plug/Ignition cable)
b.Faulty fuel delivery system (Fuel tank/Pressure regulator/Canister purge valve)
c.Clogged fuel injectors
d.Faulty fuel injectors
e.Leak in intake system
f.Leak in exhaust system
g.Faulty MAFS
If any codes relating to injectors, HO2S, ECTS or MAFS are stored, do all repairs associated with those codes before proceeding with this trouble area.
P0172
Fuel System Too Rich (Bank 1)
a.Faulty fuel delivery system (Fuel tank/Pressure regulator/Canister purge valve)
b.Faulty fuel injectors
c.Faulty MAFS
If any codes relating to injectors, HO2S, ECTS or MAFS are stored, do all repairs associated with those codes before proceeding with this trouble area.

2004 Sonata 2.7L, 155k miles
2005 Santa Fe 2.7L, 162K miles

Last edited by Nightstalker2160; 06-25-2013 at 05:12 PM.
Nightstalker2160 is offline  
#3 Old 06-25-2013, 05:20 PM
Senior Member
 
Nightstalker2160's Avatar
 
Join Date: Jul 2012
Location: Southeast USA
2004 Sonata, 2.7L auto 2005 Santa Fe, 2.7L auto
Posts: 153
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Nightstalker2160 is an unknown quantity at this point
Attached are the troubleshooting proceedures from Hyundai
Attached Files
File Type: pdf IsPrint=true.pdf (251.7 KB, 20 views)

2004 Sonata 2.7L, 155k miles
2005 Santa Fe 2.7L, 162K miles
Nightstalker2160 is offline  
#4 Old 06-26-2013, 04:46 PM
Junior Member
 
Join Date: Apr 2013
Location: louisville kentucky
Drives sonata 2003 4 cyl
Posts: 20
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
goldsonata2003 is an unknown quantity at this point
(Thread Starter)
Wow thank you very much, how would I go about testing the oxygen sensors and spark plugs? I know that about 2 months ago I had to take the car in to get a tune up as it wouldn't go about 40 mph without causing the same thing that is happening right now, before I took it in though I had a check engine light that read that my exhaust o2 sensor was faulty yet I haven't seen that check engine light since the tune up
goldsonata2003 is offline  
#5 Old 06-26-2013, 05:05 PM
Senior Member
 
jsinton's Avatar
 
Join Date: Jun 2009
Location: Inverness, Florida
'99 Elantra Wagon '03 Kia Sedona
Posts: 4,370
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
jsinton is an unknown quantity at this point
If you installed a new egr valve and solenoid, and then the problem occured, I would suspect an intake leak. If you had spark plugs replaced, that could be your problem too. You need to verify exactly what type and brand of plugs were put in because OEM plugs are critical.


jsinton is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hyundai Forums : Hyundai Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome