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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
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C1201 error code means that you have some problem in engine control system.
Possible causes for P0421 error
Warm Up Three Way Catalytic converter deterioration or malfunction
Exhaust system leaks
Loose front or rear HO2Ss
Faulty front heater O2 sensor
O2 sensors harness is open or shorted
O2 sensors poor electrical connection
The P0421 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem.
Error Code: P0421 Description:
Warm Up Catalytic Converter, Bank 1 - Efficiency Below Threshold Possible Cause:
Warm Up Catalyst Bank 1 faulty. Possible Solutions:
Check Warm Up Catalyst Bank 1 - Set Readiness.
Replace Warm Up Catalyst Bank 1.
P0305 - Cylinder number 5 misfire detected.
Probable faults and reasons:
Igniter no. 5 defective.
Ignition system malfunction.
Spark plug is short or its air too wide. (0.9 - 1.1 mm)
Weak compression.
Valve clearance less than recommended.
Engine valves and seats defective.
Fuel pump pressure too high. P0421 - Warm up catalytic efficiency is below threshold (Bank 1)
Probable faults and reasons:
Catalytic converter.
Heated oxygen Bank 1.sensor 1, 2. P1818 - Manufacturer specific code.
WARM UP CATALYST BELOW THRESHOLD - BANK 1usually this is caused be poor spark wires or plugs. If the ignition system is in poor condition or recently repaired because of misfire it could indicate that the front converter is now burnt up and requires replacement. First pls check if ur car needs a tune up? if not done since long (3yrs/60K miles), do the tune up and see if it helps. or else u will need to do as explained above.
taken from: http://forums.evolutionm.net/lancer-troubleshooting/349095-code-p0421-call-mitsu-before-you-do-anything.html Code P0421- Call Mitsu before you do anything!
Icalled my nearest dealership today and for those who dont know, if yourcheck engine light is on and its showing fault code P0421 this may befrom a factory recall on the warm-up converter and a PCM reflash.MILEAGE OF THE CAR DOES NOT EFFECT THIS RECALL. Anyone whos had problemwith a dealership not doing the repairs because of mileage needs tocontact another dealer or the owner of the dealership. This is what theservice manager told me today so though I'd share. Getting mine fixedtomorrow at 10am, I cant wait.
For more information about this code Google "Fault Code P0421" You'll get tons of information
Last edited by Swankzer; Jun 2, 2008 at 12:31 PM.
taken from: http://forums.evolutionm.net/lancer-troubleshooting/349095-code-p0421-call-mitsu-before-you-do-anything.html
Code P0421- Call Mitsu before you do anything!
I
called my nearest dealership today and for those who dont know, if your
check engine light is on and its showing fault code P0421 this may be
from a factory recall on the warm-up converter and a PCM reflash.
MILEAGE OF THE CAR DOES NOT EFFECT THIS RECALL. Anyone whos had problem
with a dealership not doing the repairs because of mileage needs to
contact another dealer or the owner of the dealership. This is what the
service manager told me today so though I'd share. Getting mine fixed
tomorrow at 10am, I cant wait.
For more information about this code Google "Fault Code P0421" You'll get tons of information
Last edited by Swankzer; Jun 2, 2008 at 12:31 PM.
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