2009 Traverse PO430

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Recently my '09 traverse threw a CEL. I checked the code with my pocket reader and it shows:

PO430: Catalyst system efficiency is below threshold. Band 2

The car runs fine. So in an effort to make a quick fix for emissions testing reasons, I put a 02 spacer on the downstream O2 sensor on bank 2. Which usually works, but the code came back.

What I find strange about this vehicle (or maybe it's more common than I know), there is a cat directly after each exhaust manifold. Then there is an O2 sensor. But there is also another cat after these two sensors. Shouldn't the downstream 02 sensor be after that? I mean, if they're really trying to figure out if the emission coming out the tailpipe are at an appropriate level....

My reader only checks codes. Bad cat? Try changing O2 sensor?

I also took it to an O'Reilys, to see if they could find out more. They just said either O2 sensor or it needs a new cat.
 
The ecm likey only monitors the front cats. You need a scan tool with live data and compare the front and rear o2 patterns. If they mimic each other (rapid high/low switching) the cat is junk. If you have a lazy front o2 sensor this can also cause this code. Again, you'd need a scan tool with live data to watch this. You'll need to monitor it as steady state cruising at highway speed. A proper functioning cat will have the front o2 rapid switching anywheee between 50-800mV and the rear a more or less flat line around 400 mV
 
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According to GM service bank 2 is the left side. Here are the instructions for system testing per GM.

Circuit/System Testing
 1. Observe the DTC information with a scan tool. Verify there are no HO2S, fuel system, or misfire DTCs set.
⇒ If there are any HO2S, fuel system, or misfire DTCs set, diagnosis the applicable DTC before proceeding with this diagnostic procedure. Refer to Diagnostic Trouble Code (DTC) List - Vehicle.
 2. Inspect and verify the following:
â—¦The catalytic converter is an original part
â—¦The HO2Sâ€2 is secure and the wiring is not damaged, or contacting the exhaust
â—¦The exhaust system for leaks, damage, or missing hardware
⇒ If a condition is found, repair as necessary.
Note: Before replacing the catalytic converter, correct any conditions that may have damaged the converter.

 3. If a condition is not located, replace the appropriate catalytic converter.
 
That's not very in depth diagnostics I would suggest watching o2 patterns long before I pull the trigger on a cat with just checking for physical damage or exhaust leaks
 
That info is directly out of GM service information. Cant get any more genuine than that.
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Circuit/System Description
In order to maintain a reasonably low emission level of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) a 3-way catalytic converter (TWC) is used. The catalyst within the converter promotes a chemical reaction that oxidizes the HC and CO present in the exhaust gas. This reaction converts the gases into harmless water vapor and carbon dioxide. The catalyst also reduces the NOx , converting the NOx into nitrogen. The engine control module (ECM) monitors this process using the post catalyst heated oxygen sensor (HO2S) signal. The post-catalyst HO2S located in the exhaust stream after the TWC, produces an output signal that indicates the oxygen storage capacity of the catalyst. The oxygen storage capacity (OSC) determines the ability of the catalyst to convert the exhaust emissions effectively. If the catalyst is functioning correctly, the post-catalyst HO2S signal will be far less active than the signal produced by the pre-catalyst HO2S.

To determine OSC, the ECM commands a rich air/fuel mixture until all oxygen is removed from the catalyst. The ECM then commands a lean air/fuel mixture and monitors the rear heated oxygen sensors to calculate the oxygen storage capacity. The catalyst is operated in this mode until one of the following conditions occur:

•The oxygen stored in the catalyst exceeds a calibrated threshold, which is determined from the rear HO2S signal.
•The rear HO2S indicates the catalyst to be completely saturated with oxygen, which is determined from the rear HO2S signal.
Conditions for Running the DTC
•Before the ECM can report DTCâ€P0420 or P0430 failed, DTCsâ€P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0100, P0101, P0102, P0103, P0121, P0122, P0123, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0335, P0336, P0338, P2096, P2097, P2098, P2099, P2195, P2196, P2197, P2198, P2232, P2235, P2237, P2240, P2243, P2247, P2251, P2254, P2270, P2271, P2272, P2273, P2297, P2298, P2626, and P2629 must run and pass.
•DTCâ€P0010, P0011, P0013, P0014, P0020, P0021, P0023, P0024, P0030, P0031, P0032, P0050, P0051, P0052, P0100, P0101, P0102, P0103, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P013A, P013C, P013E, P0130, P0131, P0132, P0133, P0135, P0137, P0138, P014A P0140, P0141, P0150, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0300, P0301-P0306, P0443, P0455, P0458, P0459, P0496, P0497, P2088, P2089, P2090, P2091, P2092, P2093, P2094, P2095, P2096, P2097, P2098, P2099, P2100, P2101, P2107, P2119, P2122, P2123, P2127, P2128, P2138, P2176, P2177, P2178, P2179, P2180, P2187, P2188, P2189, P2190, P2232, P2235, P2270, P2271, P2272, or P2273 is not set.
•The engine speed is 1,160-2,440â€RPM.
•The engine load is 13-80â€percent.
•The air flow into the engine is between 3-28â€g/s and steady.
•The ambient air temperature is warmer than −30°C (−22°F).
•The HO2Sâ€2 is at operating temperature for greater than a range of 140-210â€seconds.
•The Closed Loop fuel control is enabled.
•The calculated TWC temperature is between 500-900°C (932-1,652°F) and steady.
•The above conditions exist for approximately 17â€minutes.
•DTCs†P0420 and P0430 run once a drive cycle. The ECM will attempt to run this diagnostic up to 3â€times per drive cycle.
Conditions for Setting the DTC
The ECM determines the oxygen storage capacity (OSC) of the catalyst has degraded below a calibrated threshold. The DTC sets when the condition exists during the sample period, then a 5â€second delay for the MIL.

Action Taken When the DTC Sets
DTCsâ€P0420 and P0430 are Typeâ€A DTCs.

Conditions for Clearing the DTC
DTCsâ€P0420 and P0430 are Typeâ€A DTCs.

Diagnostic Aids
Inspect for the following conditions, which may cause a catalytic converter to degrade:

•An engine misfire
•High engine oil or high coolant consumption
•Retarded spark timing
•A weak or poor spark
•A lean fuel mixture
•A rich fuel mixture
•A damaged oxygen sensor or wiring harness
 
IF it turns out to be the Catalyst.....Which is usually the case on GM vehicles.

Your can delete P0420/P0430 from the calibration with HP-Tuners. The Interface cost ⤠$300, And the 2 credits to licence your PCM cost $100. Once you licence the PCM.....You can change the calibration as many times as you want.
Yes.....The Catalyst readiness monitor will show "ready" & will pass OBD2 emissions testing.

........Yes it's against Federal Law to tamper with Calibrations in regard to Emissions monitoring systems. Please save the morality speech for when every car in the US is required to pass emissions testing, Not just 1/3 of them.
 
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Thanks for all the advice.

At this point I think I'll just take it to a shop and see what they can tell with their equipment.

I need to invest in some better diagnostic tools.

Will post back what they find.
 
Add a second O2 spacer? Sometimes you need to use two.

If you really don't want to fix it, they also sell O2 spacers with a tiny grid of catalyst material inside. So even if the converter is bad, the sensor still sees "clean" exhaust.

At least you don't live in California where it cost me $700 to fix this code on my Mustang. I tried the spacer trick for a while but ultimately replaced the cats (all four of them, as part of the same $700 assembly, even though only one side was bad...
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) because the exhaust stunk. It doesn't smell anymore.

A cheap Bluetooth sccanner and the Torque app will allow you to view O2 graphs, fuel trims, etc. and probably cost less than your handheld scanner.
 
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Originally Posted by Anduril
Add a second O2 spacer? Sometimes you need to use two.

If you really don't want to fix it, they also sell O2 spacers with a tiny grid of catalyst material inside. So even if the converter is bad, the sensor still sees "clean" exhaust.

At least you don't live in California where it cost me $700 to fix this code on my Mustang. I tried the spacer trick for a while but ultimately replaced the cats (all four of them, as part of the same $700 assembly, even though only one side was bad...
frown.gif
) because the exhaust stunk. It doesn't smell anymore.

A cheap Bluetooth sccanner and the Torque app will allow you to view O2 graphs, fuel trims, etc. and probably cost less than your handheld scanner.


I was thinking about trying that. Thanks for the suggestion.
 
Shop just called. Said it needs a cat, or course. $700

Going to try a second spacer first.
 
As already mentioned above. Examine the exhaust for leaks. Even a very small leak aft of the last O2 sensor can set this code. I've had two flex pipes with small leaks set this code.
 
if you made your own spacer, then I think you need two. the one from ebay usually are long enough and only one is needed. this is assuming you are indeed putting it on the "correct" bank.
 
To update. It passed emissions.

The first spacer I used was one from ebay. It was about 1.5" long, but was totally open at the end. So I bought an anti fouler set, and put one of those on the end of it. Since the anti fouler has a small hole in it, instead of being open, I guess it blocked most of the exhaust.

Glad it passed. Lets see if the vehicle last another 2 years.
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