Anybody keep their downstream O2 sensors?

[SoopaCooga]

Once I had headers installed last year (along with my other goodies) I ditched the downstream O2s, in part because I didn't have enough bungs and in part because I thought the sensor check could be disabled in the tune. I am now being told that without the downstream O2s my engine could default to limp mode (i.e. crazy rich). I wouldn't think a catalyst monitor failure would trigger a change in fuel strategy, but it's within the realm of possibility.

Also, do I need to have downstream O2 sensors to pass emissions? Warmonger did not think so last year, but I'd like to hear about people's experiences. Thanks!

 

[BrApple]

the downstream sensors can be setup to be ignored in the tune. however if that is the case the cat monitor test will not run based on my observations. I never got a rich code with the B1S2 turned off.

Also I did keep the lower sensors, I just had a bung welded in for the B1S2 sensor.

I would say if the down stream sensors where removed but not turned off in the tune that is asking for troulbe.

 

[SoopaCooga]

I would say if the down stream sensors where removed but not turned off in the tune that is asking for troulbe.

In what way is that asking for trouble? The PCM would simply report that the pre-cats were not functioning up to par and/or that the sensors were not working. There should be no impact on drivability, right?

 

[BAD SVT]

Once I had headers installed last year (along with my other goodies) I ditched the downstream O2s, in part because I didn't have enough bungs and in part because I thought the sensor check could be disabled in the tune. I am now being told that without the downstream O2s my engine could default to limp mode (i.e. crazy rich). I wouldn't think a catalyst monitor failure would trigger a change in fuel strategy, but it's within the realm of possibility.

Also, do I need to have downstream O2 sensors to pass emissions? Warmonger did not think so last year, but I'd like to hear about people's experiences. Thanks!

hey soopa. am guessing u havnt dealt with the sensor issue yet. i have my downstreams on. they're right after the main cat. when i didnt have them on, my car never completed the obd II cat cycle. hence, i wasnt able to pass smog.

In what way is that asking for trouble? The PCM would simply report that the pre-cats were not functioning up to par and/or that the sensors were not working. There should be no impact on drivability, right?

generally, dysfunctional downstreams dont affect driveablility.

 

[Swazo]

I was able to turn the rear sensors all the way off with Keyser's help with PRP, and never got a CEL. I was able to get rid of them all together.

 

[BrApple]

In what way is that asking for trouble? The PCM would simply report that the pre-cats were not functioning up to par and/or that the sensors were not working. There should be no impact on drivability, right?

if the sensors are not plugged in and they are not turned off in the tune you are going to get all sorts of O2 sensors codes. Also because they are the down stream sensor it will most likely cause the pre-cat codes to set and I believe those cause the fuel safe pcm mode, and just dump fuel in.

 

[turbo_fox]

down stream 02 should have zero effect on the functions of the ECU. It's sole purpose is to monitor the cat. All the ecu does is look at it's switching as compared to the upstream 02's. If you take it out or take out the cat or anything, you will get downstream 02 codes, but they will not change the operation of the upstream, and hence not change the way the car performs. The ecu never uses a downstream 02 to control Air/fuel or put a car in limp mode

 

[SoopaCooga]

The ecu never uses a downstream 02 to control Air/fuel or put a car in limp mode

I didn't think so, but...

Without the sensors I got DTCs (of course) for bad sensor heater circuits, and the car would then operate in open loop (i.e. limp) mode.

I am going to have the sensors disabled in the tune for now. DanG tells me that I should still be able to pass emissions in Virginia. Hopefully they won't be as strict as the tester in Nevada used by BADSVT.

 

[BAD SVT]

I didn't think so, but...

Without the sensors I got DTCs (of course) for bad sensor heater circuits, and the car would then operate in open loop (i.e. limp) mode.

I am going to have the sensors disabled in the tune for now. DanG tells me that I should still be able to pass emissions in Virginia. Hopefully they won't be as strict as the tester in Nevada used by BADSVT.

long as thats the only CEL thats plaguing u, deleting them or using MILS wont be a problem. in the state of nevada, u r allowed a maximum of 2 incomplete ecu cycles. i already had the evap and P1000. so the addition of incomplete CAT cycle would make me ineligible to pass emissions. so if indeed u dont have any potential CELS, u should pass SMOG.

 

[BrApple]

I believe CT is the same, you can have two unrun tests. now that the lower O2s are both on the cat monitor test runs on my car. this only leaves the evap emission test to run, and I looked and I pasted last time without that one being complete.

P1000 says the PCM was just reset so that is most likely going to make you fail off the bat ...

 

[SoopaCooga]

The other codes I get are for the EGR: excessive flow and insufficient flow.

I have had a P1000 for six months now. :shrug:

 

[turbo_fox]

The other codes I get are for the EGR: excessive flow and insufficient flow.

I have had a P1000 for six months now. :shrug:

the egr code is probably what is causing your limp mode. I have never seen a secondary 02 code cause limp mode.

 

[SoopaCooga]

Fox, all I know is that the car stays out of limp mode so long as catalyst monitors (i.e. downstream O2) are disabled, so the EGR codes are not causing it to run in open loop mode.

Thanks, everybody, for your contributions to the discussion here.

 

[BAD SVT]

hey soopa. how about u just close ur eyes and add those sensors? it'll probably save u all this heartache. all u need are 2 bungs, a drill, and light welding equipment. install them right after ur main cat and u're good to go. ur ride will run like a top. as for the EGR problems, what steps have u taken so far to remove the CEL? fwiw, mine ran rich also when my cel was on. but i cant say for sure as all our turbo cars run rich anyway until they're adjusted.

 

[BrApple]

hey soopa. how about u just close ur eyes and add those sensors? it'll probably save u all this heartache. all u need are 2 bungs, a drill, and light welding equipment. install them right after ur main cat and u're good to go. ur ride will run like a top. as for the EGR problems, what steps have u taken so far to remove the CEL? fwiw, mine ran rich also when my cel was on. but i cant say for sure as all our turbo cars run rich anyway until they're adjusted.

only need one bung. bank 2 already has the bund for the lower O2 sensor. Its bank 1 that the lower sensor is located in the y-pipe. So I just added a bung on the y-pipe/up pipe of the kit.

 

[BAD SVT]

only need one bung. bank 2 already has the bund for the lower O2 sensor. Its bank 1 that the lower sensor is located in the y-pipe. So I just added a bung on the y-pipe/up pipe of the kit.

he's got the nautilus kit tho brian. so i'm assuming he's got a different y-pipe. at least joey didnt send mine with sensor openings:shrug:

 

[BrApple]

he's got the nautilus kit tho brian. so i'm assuming he's got a different y-pipe. at least joey didnt send mine with sensor openings:shrug:

yeah that is what I have also .... so bank 2 has the lower O2 sensor in the header, bank 1 stock is in the y-pipe so all you need to do is add a O2 sensor bung to the NPG y-pipe/up-pipe and you can install the sensor.

I can take a pic of what I did if anyone is interested.

 

[BAD SVT]

yeah that is what I have also .... so bank 2 has the lower O2 sensor in the header, bank 1 stock is in the y-pipe so all you need to do is add a O2 sensor bung to the NPG y-pipe/up-pipe and you can install the sensor.

I can take a pic of what I did if anyone is interested.

could u pls? cuz i've got both downstreams right next to each other after the cat, and i'd like to see how u did urs.

 

[SoopaCooga]

Here's my take on things

Here's my take on things

My wideband is currently in the downstream bung of the Bank 2 header.

Brapple has one catalyst monitor in the downstream bung of the Bank 2 header, and he installed a bung for the other catalyst monitor on the up pipe / y-pipe rather than on the Bank 1 header itself.

Neither of these sensors would act as catalyst monitors, of course, so if they were not disabled in the tune then Brapple would need to splice MIL eliminators into them.

He also had to add a bung for his wideband, presumably on the flex pipe ahead of the main cat. [Am I right?]

BADSVT moved both of his catalyst monitors after the main cat so they function as intended. To do this he had to extend the wiring harnesses of each sensor. Where did you install your wideband?

I am thinking about possibly splicing two sensor harnesses into one sensor so that I only need one downstream sensor but can plug it into both sockets so that the PCM is happy. Kinda crazy but it should work...

I havent' tackled the EGR yet. I may have Joey disable it until the A/F is looking good. I think I should confirm that the EGR valve will open under vacuum and that the EGR tube is not plugged (or welded shut). If both of those check out then I am going to relocate the EGR to the down pipe or even the flex pipe. Now I need three bungs on the flex pipe! That thing is gonna look like Neo in The Matrix! LOL

 

[BAD SVT]

My wideband is currently in the downstream bung of the Bank 2 header.

Brapple has one catalyst monitor in the downstream bung of the Bank 2 header, and he installed a bung for the other catalyst monitor on the up pipe / y-pipe rather than on the Bank 1 header itself.

Neither of these sensors would act as catalyst monitors, of course, so if they were not disabled in the tune then Brapple would need to splice MIL eliminators into them.

He also had to add a bung for his wideband, presumably on the flex pipe ahead of the main cat. [Am I right?]

BADSVT moved both of his catalyst monitors after the main cat so they function as intended. To do this he had to extend the wiring harnesses of each sensor. Where did you install your wideband?

hey soopa. u're absolutely right. 4got about that:troutslap:. my wideband is also in the lower part of one of the headers. thats why i have both downstreams behind the cat. which reminds me... u said u have ur wideband currently at the same spot i have mine. so it'd get its values from only one bank right? wouldnt it be more accurate placed further back so it reads from both?