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Catalytic Converter Replacement Pontiac 2008 G6 GXP 3.6L Bank 2

Thanks to neglecting the engine light (due to a bad purge valve - see my answer on that) I got code 430 indicating Bank 2 Catalytic Converter below threshold. My wife took it to a shop, who quoted $900 for the part, and $200 to install it. They said we needed the genuine GM part. Bank 2 is the front one.
I went to the dealer (Momentum Chevrolet in San Jose) and they wanted $849 for the part. This is the front one, and it comes complete with pipes and flanges.
I ordered one online for $560 + $100 refundable core charge from gmpartsdirect.com.
Replacing it was easier than I expected. I borrowed car ramps from my son, to get the front of the car about 8" higher.
First, you have to remove an air duct which connects the engine air filter to the fuel injection. It's about a 5" diameter long tube at the top just behind the radiator. Loosen 2 hose clamps and remove a bolt and one vacuum line to the crankcase.
Once that's off, you will be able to look down and see a heat shield. Remove 3 10mm bolts and move the shield out of the way. Get some Liquid Wrench and wet the 3 nuts that hold the cat flange to the exhaust manifold. Remove the 3 nuts. The studs may come out with them, but you can separate them later.
Then get under the car, nd you will be able to look up and see the O2 sensor which is threaded into the pipe just below the cat. Wet it with liquid wrench (I used a teaspoon to get it up there). I was able to loosen it with a crescent wrench. Unplug the cable before screwing it out.
Lastly, there are two 1/2 nuts holding on the flange on the other end. Again use Liquid Wrench to get those off. I had to tap the studs with a hammer to loosen the connection. Now, to get it off, you need to pull this flange forward, compressing the flexible connector.
Installing is the opposite of all these steps. Put the front end up in there first, if you have a helper to apply one or more of the nuts to hold it up that would be good. (I didn't) Then to get the back end in, you again need to pull the flange forward, compressiing the flex joint.
Tighten the nuts, reinstall the O2 sensor, put the heat shield and air tube back on, and you're finished. Relatively easy, compared to what I expected. That was yesterday, and today it passed smog! And the exhaust smells much nicer. And I saved $550! Just mailed the old part back to get my core charge back. Cheapest way was USPS ground - $24 with insurance. Printed the label using Paypal. No standing in line at the post office.

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two codes


code p1443 - Evap canister purge system mafunction.possible cause faulty Evap canister purge valve.fuel vapor hose blocked between Evap purge valve and the FTP sensor or blocked between purge valve and intake manifold or vacuum hose blocked between purge valve and intake manifold.code po430 catalytic system efficiency bank 2 below threshold.possible causes. air leaks at the exhaust manifold or in the exhaust pipes. catalytic converter is damaged.ECT OR CHT SENSOR has lost its calibration.engine cylinders misfiring or the ignition timing off.engine oil is contaminated.front HO2S or rear HO2S is contaminated with fuel or moisture.both front HO2S OR REAR HO2S is loose in mounted hole. fuel pressure is too high due to faulty fuel pressure regulator.

Jan 02, 2013 | 1996 Ford Thunderbird LX

1 Answer

code 430 and 420


Wow!, I answered this about 30 minutes ago, but somehow my answer didn't post.

Fault code 420 is Catalyst system efficiency below threshold, ( bank 1 )
Fault code 430 is the same as above but, ( bank 2 )

Fault codes do not determine what part is bad, they just reduce the field for troubleshooting.
This is what I would have checked;
1. Oxygen sensor, upstream ( meaning before the catalytic converter )
2. Oxygen sensor, downstream ( meaning after the catalytic converter )
3. MAF, ( mass air flow ), sensor
4. Idle air control sensor.

Your problem will be with the emission system.

I hope this helps you.

Feb 10, 2011 | 1999 Ford Taurus

1 Answer

I ran an engine analyst and got codes P0446 twice and code P0431 once. what does this mean.


P0431 Warm up catalytic converter, bank 2 - efficiency below threshold
Possible causes: Catalytic converter, wiring, HO2S 2

Usually caused by worn out catalytic converter, but always check fuel pressure regulator for proper operation before replacing a converter.


P0446 Evaporative emission (EVAP) system, vent control -circuit malfunction
Possible causes: Wiring, EVAP canister purge valve, ECM

May be caused by a loose or disconnected wire to the vent valve or possibly a bad valve solenoid

If you would like part locations, troubleshooting or replacement procedures, please let me know.

Dec 01, 2010 | 2004 Kia Sedona

2 Answers

Hi, I need to take my 2001 Mazda 626 4cyln for SMOG check in CA. But its check engine light is on, diagnosed as code P0421. Appreciate your help to fix this problem, or just to pass the check. Thank you.


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.

Oct 06, 2010 | Mazda 626 Cars & Trucks

1 Answer

Engine code 430


did you use oem catalytic converters????? the aftermarket converters break down very fast. thats why they are cheap. we have to replace them all the time due to bad catalytic converters.

Oct 06, 2008 | 1998 Chevrolet Suburban

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