Check engine light on, code reads p0420 - 1999 Buick Century

SOURCE: need info on codes PCM.P0134 and P0420

Both codes are for the oxygen sensors.
P0134 oxygen sensor on bank #1, sensor #1 is bad.
P0420 oxygen sensor on bank #1, the sensor down by the catalytic converter, is also bad.

SOURCE: check engine light

that code is saying that your catilitic converter is junk, but could be caused by some other problem also gas leak on exhaust system a/f sensor bank 1,2 sensor 2. heated oxygen sensor bank1 sensor 2, or the three way catilitic converter. these are the listed reasons for that code being thrown, to tell you the truth its not really that big of a deal ya know, i mean its just emissions, either the cat is bad or the oxygen sensor is bad in my opinion will it hurt the car? no, will that little light annoy the **** out of you? YES ; ) because the sensor is behind the cat it will not have any imput into your computer to change fuel maps or anything, the post sensors are only for reading if the cat is good or not, i actually cut mine off and the cat, the check engine light might always be on, but if my car messes up for some other reason then i will feel or smell it and dont really need the dummy light yea know? anyways its your choice to live with it or to take it to the shop and have your sensor tested/cat looked at, either way it wont hurt your car, if your front o2's start going bad you have to change those, but not the post cat one. dont let those shop guys bully ya into spending to much tell me what they say cause there always after an unsuspecting person's wallet, thats why i opened my own shop.

if this helped throw some blue/fix ya rating.
take care have a good day
EriK
Ez Automotive/U.S. Army

SOURCE: check engine light-on OBD code's P0420 &

The codes are Catalyst System Efficiency Below Threshold (Bank 1)&(Bank 2).

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

A code P0420 may mean that one or more of the following has happened:

• Leaded fuel was used where unleaded was called for
• An oxygen sensor is not reading (functioning) properly
• The engine coolant temperature sensor is not working properly
• Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
• Retarded spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of readings

• Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
• Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
• Inspect the downstream heated oxygen sensor (HO2), replace if necessary
• Replace the catalytic converter

SOURCE: Check Engine Light came on with code p0420. Dealer wants $3900 to fix "b2 manifold and front pipes. Does this make sense. Are their better alternatives. I left the dealership without fixing it and the

if u r have lexus or v 6 or v8 so change or check u r leak of exhouse bank #1 driver side if u all want any question send me mail [email protected]

SOURCE: Check engine light on. P0325, P0420 2000 Subaru

CODE PO420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD BANK I * CODE PO325 KNOCK SENSOR NO.1 CIRCUIT MALFUNCTION BANK NO.1 OR SINGLE SENSOR