Blackmambo90 Posted October 28, 2015 Share Posted October 28, 2015 So the car is 2005 LGT 5eat jdm swap (w/ ecu) So no cel but the ridings from rear o2 look not good - it is showing 0.8-0.9v almost all the time (on idle, on cruising, in acceleration) and its will go to 0 just when i let go the gas So te quastion is : is it a bad cat or bad o2? Or is ther some thing that i am missing? More info: Down pipe got ~ 280k I dont have a cat in my up pipe My fuel trim are all in +0.8-2.5 range (all of them was in +8 - +15 when i had a hole in my turbo inlet pipe) Exepte my fuel trim a (idle) is in +8 - +10 range (i think i have a liak after the throtlle) Link to comment Share on other sites More sharing options...
Harsho1 Posted October 28, 2015 Share Posted October 28, 2015 The only function of the rear, or secondary, or downstream O2 sensor is to check the function of the catalyst. If it is not setting a CEL then don't worry about it. This sensor does not control fuel trim AT ALL. Only the Front, or Primary, or Upstream sensor contributes to the fuel control scheme. Link to comment Share on other sites More sharing options...
Blackmambo90 Posted October 28, 2015 Author Share Posted October 28, 2015 I know, I am asking it be cose i think my cat is bad Link to comment Share on other sites More sharing options...
Harsho1 Posted October 29, 2015 Share Posted October 29, 2015 I know, I am asking it be cose i think my cat is bad If your CEL is not on you do not have a bad cat or a bad O2 sensor. What makes you "think" you have a bad cat? Sent from my Nexus 5 using Tapatalk Link to comment Share on other sites More sharing options...
mondtster Posted October 29, 2015 Share Posted October 29, 2015 If your CEL is not on you do not have a bad cat or a bad O2 sensor. What makes you "think" you have a bad cat? Sent from my Nexus 5 using Tapatalk Note that he is running a JDM ECU. Those ECUs will not light the CEL even with no catalyst. Link to comment Share on other sites More sharing options...
Blackmambo90 Posted October 29, 2015 Author Share Posted October 29, 2015 If your CEL is not on you do not have a bad cat or a bad O2 sensor. What makes you "think" you have a bad cat? Sent from my Nexus 5 using Tapatalk It is shoving 0.8-0.9 v so it is too rich afeter the cat Link to comment Share on other sites More sharing options...
Harsho1 Posted October 29, 2015 Share Posted October 29, 2015 Note that he is running a JDM ECU. Those ECUs will not light the CEL even with no catalyst. That doesn't make any sense. Why would they even have a secondary O2 sensor if it doesn't do anything? The only purpose of a downstream O2 sensor is to turn on the CEL. Sent from my Nexus 5 using Tapatalk Link to comment Share on other sites More sharing options...
Max Capacity Posted October 29, 2015 Share Posted October 29, 2015 Ask one of the Tuners. My Tuner www.tuningalliance.com is on the forum here , ask him. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Blackmambo90 Posted October 29, 2015 Author Share Posted October 29, 2015 Ask one of the Tuners. My Tuner www.tuningalliance.com is on the forum here , ask him. Is it for me or for harsho1? Link to comment Share on other sites More sharing options...
Max Capacity Posted October 29, 2015 Share Posted October 29, 2015 You, this is your thread. Most us with Tunes have that sensor deleted I think. No sure what you have in your JDM set up. Another reason we say to stay with what we all know here in the USA. Are you typing this on your cell phone or something ? (spelling errors) 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Blackmambo90 Posted October 29, 2015 Author Share Posted October 29, 2015 Yes, my cell I am thinkink of deliting my dp cat Just would like to know if it is working or not Link to comment Share on other sites More sharing options...
Max Capacity Posted October 29, 2015 Share Posted October 29, 2015 If its an aftermarket DP, I highly doubt its got an issue. If it does, IMO you have something seriously wrong that is causing it to fail. Send a log to the Tuner and ask for his thought's. I think Mike has told me the CEL's for those type codes have been deleted. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Blackmambo90 Posted October 29, 2015 Author Share Posted October 29, 2015 Nop dp is original from 2.5 gt usdm (i jave replaced the flange for the turbo) and got 280k Link to comment Share on other sites More sharing options...
Max Capacity Posted October 29, 2015 Share Posted October 29, 2015 Put a 3" dp on the car, the turbo will be much happier. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
mondtster Posted October 29, 2015 Share Posted October 29, 2015 That doesn't make any sense. Why would they even have a secondary O2 sensor if it doesn't do anything? The only purpose of a downstream O2 sensor is to turn on the CEL. I know it doesn't make much sense, but that's the way it is. I know this for a fact. I have not disabled any codes for my EJ20Y swap and it never comes up. The ECUs for the JDM engines have a much more performance oriented tune in them. Much of what people do as a first step with their US ECUs has already been done by the factory on the JDM one. Link to comment Share on other sites More sharing options...
Blackmambo90 Posted October 29, 2015 Author Share Posted October 29, 2015 It is a good idea but then i need to tune it But before the tuning i woul like to know that every think is working good on stock setup Link to comment Share on other sites More sharing options...
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