91RSCamaroSteve

Hello All,

I recently completed an LSX swap with a 5.3l into a 91 Camaro RS and I am having some issues with my front two O2 sensors.

I am running a red and blue 2002 Camaro PCM.

O2 sensors are for a 2004 5.3 silverado as thoes are the plugs I have and I have the PCM controled ground controled GND for the heater straight to GND as the Camaro PCM doesn't have the provision for that.

I initially noticed an issue when I loaded up the HPtuners scan tool and noticed both the O2s where hovering around the 450mV range. Since I was using the old O2s while I was waiting for the new O2s to come in on order, I assumed the problem was bad O2s.

What I tried is swapping in another used O2 temporary to see how it would behave and the "new one" seemed to behave like it should (jumping up and down in voltage) for about a minute or two at most and then stopped.

I then installed the new O2 sensors and they are hovering at 450mV as well.

I then tested the heater voltage and it is in fact getting 12v on ignition and I checked the O2 voltage and it was showing a different voltage then was being read by the PCM.

I was wondering if anyone had any ideas of what my problem could be before I attempt any more in depth diagnostics.

86White_T/A305

Check for good ground on the heads..and bolts on the header/manifolds are clean and not surface rusted.What o2 did you put in..i had a hell of a time fighting bad o2 problems and switched to denso units.. and it all went away.The bosch/ corvette rear o2 suggestions didnt work for me at all. I bought 2 denso universal ho2's with the same 4 pin square plugs on ebay cheap,they had a better switch count speed than the bosch and car ran smoother.Also if your not running longtube headers..or have your o2's in your custom exhaust..make 100%sure there are no weld leaks near the o2.The pcm is tuned for just front o2?

91RSCamaroSteve

If there are massive spelling and grammar mistakes I apologize in advance because I am driving and using the voice to text feature.

With regards to the exhaust I have 2002 camaro manifolds painted black so I suppose there is a possibility of grounding issues. That being said, I have a 4 pin O2 that the heater is hooked up to ground and emissions and I am getting 12v. But my question is do the O2s still need to be grounded via the block? If so I can try grounding the exhaust to frame or block to see if that fixes it.

As for O2s I went to napa and got OEM replacement I guess which are NTK something or others.

And I have the wiring for the rear O2s in place but I deleted them.

Thanks for reply

Steve

axelg89

Hi,

Did you find your troubles? I have exactly The same thing on my ls1 swap..

Thanks

91RSCamaroSteve

I have yet to find the issue yet because I have been tasked out for work for the last little while and didnt have much time to diagnose yet. But I'll probably start again this week.

I am going to look at the wiring for the heater to ensure its getting enough current and then im not sure what I'm going to do but I'll keep you posted if I find anything out.

axelg89

Will keep you posted on what I find too. The heater is pretty easy to check as you should feel it getting warmer after a while with the ignition on. Also the o2s should show readings after the engine has been on for a while even if heaters are not working. I think this would probably be a ground issue as that's the only common connection between the o2 sensors. Feels strange that both new o2 sensors would be faulty or both side wiring...

86White_T/A305

You shouldnt need to ground the o2 to the block.They should have efficient ground in the harness.Was the harness modified at all or extended,this has been known to cause issues due to exhaust heat and poor wiring connections.

Also which type of o2 are you using? Is the sensor tip short and has a small single slit opening,or does it have small openings all around? The delco replacements I first had were the short style with single opening and did the same thing..read slow and hoovered around 450mv no matter how hot or cold.Took them back and exchanged them..1 worked good.. another still did the same thing and I was getting o2 codes for slow switch counts.Then i switched to bosch sensors which worked semi ok for about 3 weeks before i was getting codes again.I finally settled on denso..made my own extension harness..heat shrinked etc.problems gone.

axelg89

I have these, strange with new producs not working:
http://www.ebay.com/itm/SMP-SG274-OXYGEN-SENSOR-FOR-CADILLAC-SEVILLE-1995-1999-/160862862632?pt=Motors_Car_Truck_Parts_Accessories&hash=item25742c7d28&vxp=mtr
Sorry 91RSCamaroSteve, I'm making so many posts here I almost feel like I'm steeling your thread but I think we share our goal here...

I know that the o2 has its own "ground" from the PCM and that the heater has its own 2 wires (ign, ground). Then there is the high signal left where the PCM should recieve the o2 signal from the sensor if I understand correctly?

The thing that makes me confused is that I get a ground from only one wire (heater circuit) and get a voltage from the rest of the pins (12+ for heater, ~5v from high signal pin, ~1.4v from low signal pin).

Is this normal that the PCM outputs voltage to the low and high signal pins?

If you measure your pins 91RSCamaroSteve, do you get the same voltage? Could anyone that has a functioning o2 measure theirs?

Thanks

86White_T/A305

Its not as strange as you think,head over to ls1tech and the amount of o2 threads is quite high..with and without headers.Its a common issue with random results of how to find a solution. I think the quality of o2 plays a role,placement of the o2 is very important,as is making sure you dont have an exhaust leak near the o2 bung.Aside from checking the harness for any signs or damage I got lucky having my issue being fixed.But I also went months trying things out as I could.My tuner also mentioned ways of being able to tune the sensors,setting the thresholds and adjusting how soon to command o2 readings etc in some cases.Good luck,I cant meter my o2 wires..nor do I want to probe any wiring regarding them anymore lol..they aint broke and I dont wanna fix them again :P

cam-

Stay away from Bosch, stick with OEM AC Delco ( Denso iirc . C6 Vette rear O2's seem to work best for me ( holes all around the sensor tip like bottom pic below )



If your tune is on the rich side you will take out O2's quite rapidly. Ive taken out more than one within a day or two of tuning from being too rich. They are fairly sensitive and with headers the distance from heat increases that issue. The truck type which have only a few holes at the tip are too slow responding for high performance use imo. They work, but respond slow

91RSCamaroSteve

Thanks a lot for all the responses. I was in the middle of a move and finally finalized my move and was able to re-visit this issue.

I finally resolved this issue.

As I stated before I was trying to use the 04 style O2s for the shear fact that the engine was originally an 04 and the wiring harness had those style plugs. What completely slipped my mind was that the O2s were designed with a PCM controlled heater meaning that the heaters were designed for 5V. Because I was using a 02 Camaro PCM (12V Ign controlled heaters) I had to hook the O2s up the a 12V Ign source.

All that to say that I believe the 12V Ign was killing the heater and O2s. So what I did was change over to the 02 Corvette Rear O2s and it now works perfectly.

I hope this helps anyone that encounters this problem. It seems extremely obvious once you realized the issue but it is easy to overlook the obvious especially considering you just completed an LSX swap and want to enjoy it.

hat it boils down to is getting the correct parts for the correct job which is not what I did.