In a Saturn SL2 1998, I have the check engine soon light on. The codes readings show P0133 and P0422.

Need a different mechanic

They never tested anything,
if you got codes

all part stores will scan the car for free and I need the codes please

P0401 is EGR valve, low circulation detected.
P0420 Catalyst system.
P0133 is O2 sensor bank 1 sensor 1.
All these codes are emissions related, so i would start with the EGR valve, it's probably clogged with carbon. The catalytic converter could be also, check that for excessive backpressure. The oxygen sensor can be tested, replace if needed. Good luck, i hope this helps.

P0422 - Catalyst below threshold.

Catalytic converter is clogged or out of medium.

Replace it.


ACTUAL DIAGNOSTIC:

Fault Code Definition
Code P0422 indicates that the Bank 1 Main Catalytic Converter's emissions efficiency has fallen below the minimum allowable limit. This threshold is tracked by a Catalyst Monitoring Oxygen Sensor located on or near the outlet of the Catalytic Converter.

Symptoms

* Check Engine Light will illuminate
* In many cases, no abnormal symptoms may be noticed

Common Problems That Trigger the P0422 Code

* Defective Catalytic Converter
* Engine misfires have damaged the Catalytic Converter
* Internal engine damage resulting in high oil consumption and/or a leaking Head gasket has damaged the Catalytic Converter

Common Misdiagnoses

* Oxygen Sensors are replaced when the real problem is a damaged Catalyst
* Catalyst is replaced when the real problem is internal engine damage, which is producing elevated emissions levels
* Catalyst is replaced when a misfiring engine is the real problem



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P0422 - Catalyst below threshold.

Catalytic converter is clogged or out of medium.

Replace it.


ACTUAL DIAGNOSTIC:

Fault Code Definition
Code P0422 indicates that the Bank 1 Main Catalytic Converter's emissions efficiency has fallen below the minimum allowable limit. This threshold is tracked by a Catalyst Monitoring Oxygen Sensor located on or near the outlet of the Catalytic Converter.

Symptoms

* Check Engine Light will illuminate
* In many cases, no abnormal symptoms may be noticed

Common Problems That Trigger the P0422 Code

* Defective Catalytic Converter
* Engine misfires have damaged the Catalytic Converter
* Internal engine damage resulting in high oil consumption and/or a leaking Head gasket has damaged the Catalytic Converter

Common Misdiagnoses

* Oxygen Sensors are replaced when the real problem is a damaged Catalyst
* Catalyst is replaced when the real problem is internal engine damage, which is producing elevated emissions levels
* Catalyst is replaced when a misfiring engine is the real problem



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a po410 code is, Secondary Air Injection System Malfunction.

both oxygen sensor codes

is this a 4 or 6 cylinder?
if a 4 cylinder it will only have 2 o2 sensors
V6 will have 4 o2 senors which the sensor will be the right side of the engine first sensor.
1st sensor on exhaust, I recommend if you change one change all, as this will make the computer when it rechecks the system you have all clean/fast responding sensors.

if you have a slow response it means the sensor is dirty and not reading well, which is usually caused by minor misfires that the engine computer dismisses, so a tune up would be recommended too.

I just came from an Autozone, and then spoke with 2 Hyundai dealership service departments and they all three stated the P0113 code is the Intake Air Temperature sensor (IAT, also referred to as the Mass Air Pressure - MAP - sensor) on the engine, not an O2 sensor found in the exhaust system.

Based on what the tech manuals say I would change the DPFE sensor for the EGR Valve, careful not to tear the special silicone rubber hoses that go to it from the exhaust, as a Ford dealer tech I saw these codes allot, and the DPFE sensor was almost always the issue or the hoses going to it.