I have a 2005 Hyundai sonata and the. Voltage on my oxygen sensors o2s12 and o2s12 read .410 and do not fluctuate does that mean they are bad or would that be a converter I am throwing a p0420 p0050 p0150 and also a p0128 which is

p0134 is bank 1 sensor 1, that is the sensor on bank 1 before the catalytic converter, it is not being read, i would recheck the connection and or check the wires for damage. As for the P0350 that is Ignition Coil Primary/Secondary Circuit Malfunction make sure both of the wires are plugged in all the way and there is a good connection. If the voltage is low and the PCM can not read it it will trip the light

Locate the two oxygen sensors on either side of the Sonata's catalytic converter on the exhaust manifold. The Sonata's oxygen sensor is gold and shaped liked a spark plug.

2 Remove the Sonata's wiring harness from the end of the two oxygen sensors using your fingers. Do not damage the end of Sonata's wiring harness.

3 Remove the two oxygen sensors from the Sonata's manifold using the oxygen sensor wrench.

4 Apply the anti-seize compound to the threads of the Sonata's two new oxygen sensors.

5 Install the two new oxygen sensors to the Sonata's manifold using the oxygen sensor wrench. Re-attach the wiring harness to the two new oxygen sensors using your fingers.

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

Technical Description

Catalyst System Efficiency Below Threshold (Bank 1)
What does that mean?

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.
Symptoms

You will likely not notice any drivability problems, although there may be symptoms.
Causes

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

Possible Solutions

Some suggested steps for troubleshooting a P0420 error code include:

* 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

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.


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4 or 6 cyl 4 cyl there are 2 both located in the exaust manifold one on top one below,the cat converter, 6 cyl there are 4 of them

Go to www.hmaservice.com and register( Vehicle by VIN). Afterward, you have access to shop manuals, service bulletins, wiring diagrams, etc. about your vehicle.

did you pick up a fault code to explain your action as i dont believe the oxygen sensor is at fault.it might be that one of your other sensors is at fault.the 02 sensor only reads the emmition gasses but will not cut the engine.plse get the fault codes.

that's exactly what should happen if you have it showing F instead of C (or is it viceversa?)

I just did the math

Catalyst System Efficiency Below Threshold (Bank 1)

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


To Do list

* 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

might have a oxygen sensor that went bad, take it to advance auto the trouble shoot for free