03 santa fe code p0421 for warm up catalyst below bank 1is it converter sensors whats bank 1 converter location compared to bank 2 is there 2 banks or converters would it be upstream or downstream if it were converter is there diagram of all help this code stinks and my 10 day is running out fast

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.

P0421 code is that the cat. converter is below efficiency. 99 per cent o the time the cat. needs to be changed. but if you have a scan tool watch both bank 1 O2 sensor 1 and bank 1 sensor 2.
cold they should be almost the smae but when its at operating temp, and running down the road at crusie speed the frt o2 should switch rapidly between .150 mv. and .850 mv. and the rear o2 should read about .600 mv. if they read the same the cat is ng and will have to be replaced.

Hi there:DTC P0421 - Warm Up Catalyst Efficiency Below Threshold (Bank 1)


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.


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.



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.


Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

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Hi there,

P0421 = Warm Up Catalyst Efficiency Below Threshold (Bank 1)

This means the HO2 (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.

P0421: Warm Up Catalyst Efficiency Below Threshold (Bank 1).

This could apear because of a bad O2 sensor on the catalytic converter on bank 1.

Or The catalytic converter is no longer functioning properly.

Hope this helps you. Good luck bro

CODE P0421. DEFINITION-CATALYST EFFICIENCY LOW-BANK 1. EXPLANATION-THE OXYGEN SENSORS MONITOR THE CATALYTIC CONVERTERS ABILITY TO STORE OXYGEN. PROBLEM CAUSES- 1. CATALYTIC CONVERTER DEFECTIVE (FAILURE POSSIBLY DUE TO #2,3, OR 4) 2. ENGINE MISFIRE OR RUNNING CONDITION. 3. LARGE VACCUM LEAK 4. ENGINE OIL LEAKAGE INTO EXHAUST-VALVE GUIDE SEALS, PISTON RINGS. THE PCM HAS DETERMINED THAT THE WARM UP CATALYST EFFICIENCY FOR BANK 1 IS BELOW TRESHOLD FOR THE CURRENT ENGINE OPERATING CONDITION. (BANK 1 IDENTIFIES THE LOCATION OF CYLINDER #1, WHILE BANK 2 IDENTIFIES THE CYLINDERS ON THE OPPOSITE BANK).

replace O2 sensors, or your Catalytic Converter.

po421 warm up catalyst efficiency below threshhold bank 1, 431 same on bank 2..

If you have more than 60K miles start by replacing the Oxygen sensor(s) that is(are) installed after the catalytic converter(s). 
P0421: Warm up catalyst efficiency below threshold. This code means that the computer is detecting the catalyst not warming up to full function quickly enough based on information from the post cat O2 sensor. 

Good luck and hope this helps. 

code p 0421 refers to warm up cat converter bank 1 --- efficiency below threshold ===causes ---cat converter---wiring ---HO2S (heated oxygen sensor )
there are not 4 oxygen sensor as you have been told but just 2 oxygen sensors located after each of the cat converters
The other 2 are heated oxygen sensor which are located in the exhaust manifold or exhaust pipe before the cat converters
heated oxygen sensors do a completely different job to the O2 sensors in that they report to the ECM, the combustion gas mixture so the the ECM can adjust the mixture for max performance
The oxygen sensors (O2) read what is left after the cat converters have done their job and report to the ECM so that it can fine tune the mix
IF you didn't replace the correct cat converter then that will make the code come back
If you just replaced the O2 sensor , well that doesn't even figure in the problem