P0430 after secondary air bypass? (1 Viewer)

Joined
Jan 20, 2019
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19
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PDX
Hey all,

I put in the Hewitt Tech SAIS bypass a while back to fix the various issued associated with that secondary air system on an 05 GX. This included some block off plates and a proxy pack or two. All dash error lights went off after the work.

A short time later, check engine came back on. I finally got a chance to pull the code and it is a P0430, passenger side cat showing as needing replacement. No having a ton of knowledge on these trucks, is it possible that this 430 code is at all related to the bypass kit install? As you all know, replacing a cat on these engines is far from cheap.

Thanks for any thoughts!
 
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Joined
Mar 3, 2020
Messages
21
Location
Connecticut
Unlikely it is related to the bypass. Most likely it is the O2 sensors or cat related. How many miles and in what condition is the exhaust? What is your typical driving situation?

The code is due to a fault in the catalytic converter efficiency, so the downstream O2 sensors compared to the up stream sensors are showing that the cats are not working effectively. The reason I ask about the driving situation is that many cat converters work on a heat basis, and the cat "catches" unburned fuel (and NOX and CO) and acts as the catalyst to convert these gases to O2, N2, CO2, and H20. There is a minimum operating temperature for the Cat to work effectively, and a lot of short driving trips can lead to issues in the long term.

Actually, the SAIS is intended to "light up" the cats on cold start up, but I have no idea on the timing of the system checks.

Personally, I like to make sure I get a periodic long drives in, make sure everything gets up to a good temperature to reduce the amount of water vapor in the engine and exhaust. Also like to get a good WOT on ramp run in (once everything is up to temp) once in a while to ensure a good dose of high temp exhaust is flowing through the system and burning of any trapped hydrocarbons in the cat. Do I know if that works for sure, no, just anecdotal, but it is fun :)

My advice, clear the codes, visually inspect the O2 sensors and exhaust and go from there.
 
Joined
Jan 20, 2019
Messages
19
Location
PDX
158k on the truck and the exhaust is in good shape. I had the O2 sensors looked at (they seemed to check out), and will be getting a second opinion before deciding on next steps.

I do not drive a ton, and usual trips are fairly short. I did one nice long road trip in the early fall, and like to get on the throttle on those onramps etc when things are warmed up.

Overall, I really enjoy the truck and don't mind putting some time/money into it, as long as I don't keep getting hit with some of these larger ticket items.
 
Joined
Mar 3, 2020
Messages
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Connecticut
Depending on the frequency of the codes, I wouldn't worry about the cats yet.
If it continues to be an issue, replacing the 02 sensors is the next option I would explore.
 
Joined
Jan 17, 2005
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5,619
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Southern Colorado
Look up 'spark plug antifouler mod' and install one. It makes the rear-most oxygen sensor less effective by spacing it away from the exhaust stream, which causes the computer to believe the cat is working. My brother has done this on several Toyotas and a Tahoe and it has worked every time.

 
Joined
Feb 8, 2017
Messages
73
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SC
Really common problem. For me it has always been an exhaust leak or bad 02 sensors. There is no way for the bypass kit to directly affect the rear 02 sensor or catalyst. We do see occasionally when you reset the codes by disconnecting the battery that the sensors can't get back to where they were and then throw the codes. Sometimes the sensors can't get back to where they were reading before fast enough and then it throws the codes.
Make sure you check and fix ANY exhaust leaks before the rear 02 sensor first. I have a problem knocking the donuts gaskets out or loose and even keep spares for them when I go offroading. If that doesn't do it I then replace the rear 02 sensor but only for the side throwing the code so P0430 = Bank 2 (passenger side). If it still comes back after that I then replace both upstream 02 Sensors as a pair. I don't hesitate to replace the upstream as a pair if they are original and you are in the 150k+ mileage range. I consider them a tuneup item at that point anyways and have seen it make a big difference when I am fixing up a 4.7L. Of the four or so times I have dealt wiht those codes it has been exhaust leaks twice, a rear sensor once and I replaced all four 02 sensors once. I have replaced upstream 02 sensors a couple of other times but not for catalyst inefficiency codes.
Do yourself a favor and buy DESNO only sensors and get them from an authorized dealer, not ebay or amazon. If you use factory Denso sensors and still have the code pop up then consider replacing the passenger side cat or using one of the other methods like the anti fowl or rear 02 sim.
Some people claim the cat cleaner addatives work but I have never used any.
 
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