Aftermarket cats, 2nd O2 sensor location, P0420 P0430

Can't seem to find a diagram anywhere. 2nd time to replace stolen cats. Had aftermarket magnaflo cats put in with new O2 sensors this time and the downstream O2 sensors are screwed in the cat. It seems like the original O2 sensor had a gasket and was bolted into the pipe just down from the cat, from some pictures I have seen. Because these sensors are located in the cat would that be causing the P0420 and P0430 error codes? I've read that some people have put extensions on the O2 sensors to get them to not throw the error code, would this possibly be a fix? Any advice would be greatly appreciated!

 

@5N0W808 has his downstream o2s in his cats I believe

Another member told him that it was unlikely that the code would ever clear without some sort of tomfoolery. Hopefully he will chip in at some point as I don't remember the details.

 

The auto parts store pulled my CEL codes, P0135, P0155. 135=O2 Sensor Heater bank 1 sensor 1. ?
155= O2 sensor Heater bank 2 sensor 1
My question now is how the heck do I know where the 2 O2 sensors are so they can be changed?

Thank you,
DC Miller

 

On a 4.7 Eng, Bank 1 is driver side, Bank 2 is passenger side.

Sensor 1 is upstream of CAT, Sensor 2 is downstream of CAT

 

Two things to add to what Bubba said.

First, USE DENSO PARTS on this one. Specifically, it's one of the "only use OEM for this specific item" components. And buy from a trusted source (i.e. not Amazon, not eBay) to ensure you're getting genuine parts. Summit Racing is one of the cheapest places to get Denso parts and has a 10% off coupon (code: SP27KLH) if you order in the next 36 hours! You should get really rapid shipping too.

Second, I personally recommend replacing in pairs. If the upstream or downstream is dying, replace both on that side. Reality is, the other one is probably gonna die soon, and there are also cases where one sensor will mask the actual failure of the other sensor, causing you to continue throwing codes.


It really helps if you put your engine (V8/V6) in your truck info details of your profile. Also helps if you put in 2WD/4WD. There are differences in what folks here will recommend to you based on those details. Like... Downstream sensor is different between 2WD and 4WD...

If you're 2WD in 2001 models, here are your parts:

• Upstream: https://www.summitracing.com/parts/dnp-234-4169
• Downstream: https://www.summitracing.com/parts/dnp-234-4154

If you're 4WD in 2001 models, here are your parts:

• Upstream: https://www.summitracing.com/parts/dnp-234-4169
• Downstream: https://www.summitracing.com/parts/dnp-234-4162

 

Thank you both very much, so basically I should just replace all 4 of them and get it out of the way.

DC Miller

 

I mean, you may want to just replace the two on that single bank, then buy the other two for when the opposite banks barfs if you want full longevity.

But with 10% off, you're looking at around $200 to not think about this issue again for (likely) another 20 years by using OEM parts... assuming nobody steals your cats. And for the record, I wouldn't wish that pain on anyone.