Moving the 2nd O2 sensor with catless header - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

gutbuster · 03-03-2018, 07:21 PM

Ok, here is the dealio. The OEM header with cat will be replaced with a catless header and tune using Ecutek architecture. It has two bungs to install O2 sensors. The plan is to use the 2nd bung for the O2 sensor #1. The OEM front pipe with cat will remain. I could Tig weld a bung just after that cat. O2 sensor #2 would go there (with the wires extended). The tune would be set up to NOT suppress the CEL for Cat function (I think it is p0420)

So I would end up with a sensor upstream and downstream of the remaining cat.

The reason I do not want the CEL suppressed is that the OBD2 readiness monitor for cat function will never go to a ready state if the tune suppresses the CEL. In NYS the annual DMV inspection will only allow you 1 "not ready" monitor.

I do not want to spend a day every year screwing around swapping the system back and forth and reflashing the ECU.

Has anyone done this and made it work (No CEL AND no more than 1 monitor pending?)

https://i.imgur.com/XLb51rJ.jpg

gutbuster · 03-03-2018, 07:22 PM

can someone help me get the image to show?

x808drifter · 03-03-2018, 08:22 PM

Put [img]link to pic[/img]

Or even easier click the add photo button and paste the link in the box.

steve99 · 03-03-2018, 08:26 PM

Why not just use the two standard bungs in new catless header, but install an 02 spacer in rear 02 sensor.

much less hassle and will have about the same chance of wrking as moving the rear 02 sensor.

the ecu is looking for specific readings from the sensors anything but stock cat may trigger CEL P0420

https://www.ebay.com.au/sch/i.html?_...pacer&_sacat=0

Kodename47 · 03-04-2018, 06:47 AM

That would work. It shouldn't matter which one you use for the primary O2 sensor, but depending on the manifold design you would want the one after all runners have merged and if both are after the merge the one closer to the engine is preferable.

kevman_101 · 03-05-2018, 03:12 PM

I moved the rear sensor on my old Sentra Spec V with hair dryer wire... Worked perfectly. We cut a bung off the stock header, punched a hole behind the 2nd cat, which was an aftermarket high flo cat, and welded it on. Then extended the wire for the 2nd sensor with hairdryer cord and it never gave me a CEL.

03-04-2018, 06:47 AM	#5
Kodename47 Senior Member Join Date: Oct 2012 Drives: UK GT86 Location: UK Posts: 3,040 Thanks: 185 Thanked 1,633 Times in 1,113 Posts Mentioned: 156 Post(s) Tagged: 1 Thread(s)	That would work. It shouldn't matter which one you use for the primary O2 sensor, but depending on the manifold design you would want the one after all runners have merged and if both are after the merge the one closer to the engine is preferable. __________________ .: Stealth 86 :. Abbey Motorsport/K47 Tuned Sprintex 210 Supercharger Kodename 47 DJ: Soundcloud / Instagram / Facebook

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03-03-2018, 07:21 PM	#1
gutbuster Senior Member Join Date: Aug 2013 Drives: 13 FR-S Location: NY Posts: 113 Thanks: 22 Thanked 44 Times in 27 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	Moving the 2nd O2 sensor with catless header Ok, here is the dealio. The OEM header with cat will be replaced with a catless header and tune using Ecutek architecture. It has two bungs to install O2 sensors. The plan is to use the 2nd bung for the O2 sensor #1. The OEM front pipe with cat will remain. I could Tig weld a bung just after that cat. O2 sensor #2 would go there (with the wires extended). The tune would be set up to NOT suppress the CEL for Cat function (I think it is p0420) So I would end up with a sensor upstream and downstream of the remaining cat. The reason I do not want the CEL suppressed is that the OBD2 readiness monitor for cat function will never go to a ready state if the tune suppresses the CEL. In NYS the annual DMV inspection will only allow you 1 "not ready" monitor. I do not want to spend a day every year screwing around swapping the system back and forth and reflashing the ECU. Has anyone done this and made it work (No CEL AND no more than 1 monitor pending?) https://i.imgur.com/XLb51rJ.jpg __________________ Former rides: 78 Scirocco, 80 Corolla, 79 Celica, 91 CRX, 90 CRX-Si,02 GTI, 87 944s, 86 911 3.2 Carrera, 03 MR2 Spyder

03-03-2018, 07:22 PM	#2
gutbuster Senior Member Join Date: Aug 2013 Drives: 13 FR-S Location: NY Posts: 113 Thanks: 22 Thanked 44 Times in 27 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	can someone help me get the image to show? __________________ Former rides: 78 Scirocco, 80 Corolla, 79 Celica, 91 CRX, 90 CRX-Si,02 GTI, 87 944s, 86 911 3.2 Carrera, 03 MR2 Spyder

03-03-2018, 08:22 PM	#3
x808drifter LMGTFY Join Date: Mar 2016 Drives: 13 FRS, 91 Miata Location: Lava Town, HI Posts: 2,776 Thanks: 5,561 Thanked 3,650 Times in 1,625 Posts Mentioned: 15 Post(s) Tagged: 0 Thread(s)	Put [img]link to pic[/img] Or even easier click the add photo button and paste the link in the box.

03-03-2018, 08:26 PM	#4
steve99 Banned Join Date: Dec 2013 Drives: FT86 Location: Australia Posts: 7,996 Thanks: 1,035 Thanked 4,993 Times in 2,983 Posts Mentioned: 598 Post(s) Tagged: 2 Thread(s)	Why not just use the two standard bungs in new catless header, but install an 02 spacer in rear 02 sensor. much less hassle and will have about the same chance of wrking as moving the rear 02 sensor. the ecu is looking for specific readings from the sensors anything but stock cat may trigger CEL P0420 https://www.ebay.com.au/sch/i.html?_...pacer&_sacat=0

03-05-2018, 03:12 PM	#6
kevman_101 Senior Member Join Date: Apr 2013 Drives: 2013 Scion FRS Location: Bathurst New-Brunswick Posts: 222 Thanks: 3 Thanked 101 Times in 61 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	I moved the rear sensor on my old Sentra Spec V with hair dryer wire... Worked perfectly. We cut a bung off the stock header, punched a hole behind the 2nd cat, which was an aftermarket high flo cat, and welded it on. Then extended the wire for the 2nd sensor with hairdryer cord and it never gave me a CEL.

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