2001 Tahoe no check engine light. will not pass smog due to stored trouble codes. air valves , catalytic converter

Question edited for clarity.
Question moved to model category.

Did you clear the code with a Scan Tool after replacing the valves?

The 1998-2001 Chevrolet Tahoe has a known issue with the air pump check valve which causes illumination of the check engine light. There are no notable symptoms, but the vehicle will not pass state inspection or smog testing. When the valve fails, it sticks closed, and the computer sets the code P1416.Dec 10, 2016

Check Engine Light and Code P1416 on Chevrolet Tahoe

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Definition of P0420 is catalyst below threshold. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). Catalytic converters are not normally a "wear" type item, that is they are not deisgned to wear out and need replacement. If they have failed, it is likely due to something else that caused it to fail.

P0447 Evaporative Emission Control System Vent Valve/Solenoid Circuit Open. The Powertrain Control Module (PCM) has detected an open within the circuit that controls the vent valve or solenoid for evaporative emission systems vapor.

Read more at: http://www.obd-codes.com/p0447
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If the check engine light was on DTC'S - diagnostic trouble code's should be stored . If the light was on , disconnecting the battery won't do anything . Diagnostic's need to be done . Sounds like you have no clue , so best advice , take it to a qualified repair shop .

Codes and the CEL can be erased with the same scanner used to retrieve the codes. It is a separate function of scanners.

Dear Sir:

EGR Ehaust Gas Recirculation system.the basic component is vacuum-operated control valve that recirculates the exhaut gases through the engine the engine intake manifld and cylinders where they recombine with the incoming air/fuel mixture.The check need special equipment, to some workshop.
sincerely. God bless you.

ernesto cuadra
managua, nicaragua. c.a

see the diagram for details.

The first thing i would do is take your car to autozone and have then scan the computer for trouble codes they do this procedure for free, then you can better diagnose why the check engine light on your car is illuminated, as far as failing your smog test that could be a number of reasons why that happened, you could have a bad O2 sensor, a bad catalytic converter, your engine can be burning oil due to worn or bad piston rings or bad valve guide seals, but i would first figure out why the check engine light is on it could be a simple fix or a major repair, theres no point in guessing until the computer is scanned further...

Here are a few things to look at:
Have you replaced the air filter? Have a compression test done on the engine, could possibly be a leaking vale. If any vacuum hoses have been removed from the engine they will have to be re-installed. Solid Lifters out of adjustment can cause incomplete combustion. Make sure engine is reaching proper operating temperature (eg. thermostat). Do not use low grade (octane) fuel for test.
Clean oil, tire pressure, brake drag?, every little thing counts.

CODE P0421. DEFINITION-CATALYST EFFICIENCY LOW-BANK 1. EXPLANATION-THE OXYGEN SENSORS MONITOR THE CATALYTIC CONVERTERS ABILITY TO STORE OXYGEN. PROBLEM CAUSES- 1. CATALYTIC CONVERTER DEFECTIVE (FAILURE POSSIBLY DUE TO #2,3, OR 4) 2. ENGINE MISFIRE OR RUNNING CONDITION. 3. LARGE VACCUM LEAK 4. ENGINE OIL LEAKAGE INTO EXHAUST-VALVE GUIDE SEALS, PISTON RINGS. THE PCM HAS DETERMINED THAT THE WARM UP CATALYST EFFICIENCY FOR BANK 1 IS BELOW TRESHOLD FOR THE CURRENT ENGINE OPERATING CONDITION. (BANK 1 IDENTIFIES THE LOCATION OF CYLINDER #1, WHILE BANK 2 IDENTIFIES THE CYLINDERS ON THE OPPOSITE BANK).

replace O2 sensors, or your Catalytic Converter.

P0505 Idle Control System Malfunction

IACV or Idle Air Control Valve if equipped is malfunctioning.

P0420 Catalyst System Efficiency Below Threshold (Bank #1)
The Catalytic converter is not working up to par in Bank#1.

I think this will point you in the right direction..

are you getting any codes or lights on i would change catalytic convertor probably clogged .mine barely passed on my 1999 and looking at the test it was pointing towards catalytic good luck shop around for good price