I have two check engine lights on P0303 and P0422

you have multiple cylinder missfire 1,2,3,5 check your spark plugs, plug wires and coils could even be a o2 sensor

P0422 Buick - 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



Thanks for using FixYa - a 4 THUMBS rating is appreciated for answering your FREE question.*&#$%

Have vehicle scanned for codes at Autozone its free and do the repairs the codes list.

P0171 is LEAN and P0303 is misfire number 3 cyl. Its time to stop guessing and pay for a correct diagnosis. Find a shop that works on VW and has the tools to work on it. DO NOT put those Bosch Platinum Spark plugs in that Ottozone tries to sell everybody.

this means your catalytic converter is no longer doing wut it supposed to! needs replaceing ! u can drive the car! but get it done asap

• 16706 P0322 Ign./distributor Eng. Speed Inp. Circ No signal
• 16687 P0303 Cyl. 3 Misfire Detected
  
• 16806 P0422 Main Catalyst, Bank 1 Below Threshold

P0322 Could be caused by a faulty Engine Speed Sensor also known as a Crankshaft Pos./Engine Speed Sensor.

P0303 Might have a faulty #3 Fuel Injector, Faulty spark plug and/or faulty spark plug wire and connectors.

P0422 Either your front 02 sensor is faulty and/or your catalytic converter is fried and needs replacing.

P0422 does not refer directly to an O2 sensor. That is a different code. P0422 is about the CAT. How many miles you have it and when did you buy it? VW has extended a warranty on the New Beetles for the CAT to 120,000 mi and 10 yrs. I had the same code and took it to the dealer to see if they'd replace the CAT in the warranty and they did. I had 47,000 miles and bought it at the end of Aug 1999, so I just slipped through. They replaced the downstream O2 sensor as well - all free of charge!

the car has mis fired with mean an injector has gone bad or it needs spark pluges and wires i bet it needs the plugs but it could also be both replace the plugs and wires then go from there