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Warm Up Catalyst Efficiency Bank 1 Below Threshold If you ran you car for a long period with it missing, then you probably damaged your catalytic converter.
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.
If this is a V6 model, Bank 1 would indicate one side of the motor. Also, if it's the V6 model, I believe there are 3 O2 sensors, one per Bank, and one downstream(post-cat). If it is the V6 model, and it indeed is Bank 1, then just replace the O2 sensor, that's the most likely cause.
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.
you have the same engine as my 2003 Galant, this should help... http://www.alldatadiy.com/alldata/AFI~V11366605~C40797~R0~OD~N/0/89012112/98644464/98644470/110938985/34853741/34857029/34857030/34857663/122915129/135964338/135975025
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