I just got done with a recent engine build and now my secondary 02 sensors voltage reads .280v all the time. I changed the sensors still the same. If you unplug them it still shows .280v the only way we have got it to change is to ground it to the chassis off the plug.

Any thoughts? there is not CEL and the car seems to drive fine.

 

The only sure way to read an O2 sensor is with a scope, volt meter wil lie. The 02 sensor creats its own voltage, zirconium and platinum junction react to the O2 in the exhaust gas. With a scope, you'll see a sawtooth wave form, peak to peak. Volt meter reads RMS.

 

If only we all had oscopes laying around to perform signal analysis on anything and everything.

 

Some of us do

 

I have been watching the voltage with a scan tool and with cypher. I can probably get my hands on a scope. however the 02 sensors are new so I am not sure it is in the sensor. wiring maybe?

 

If your running Innovate widebands, they had quality control issues with theirs LM-1 modules. The good news is they're great about replacing faulty equipment.

 

nice man

 

maybe I should have been more specific. Its a 2003 so no FACTORY widebands. I am running an aem wideband that I am not having any issues with.

The problem lies within the secondary 02 sensor circuit. Like stated before I have no check engine light. Monitoring the voltage with either a scan tool or cipher the voltage reads .280v this is with new sensors. The weird thing is if I unplug them it still shows .280v but.. if I ground out the circuit at the sensor side of the plug it will show 0v.

I do happen to have some custom CEL fix bungs on them but I would think it would effect them like that esp. since it still shows voltage unplugged.

Anything?

 

What's wrong with .280v rms? How do you know that's not what the narrow bands are supposed to read? And finally, why are you trying to fix something that isn't broken?

 

well I am fighting a few issues related to tuning I doubt this has anything to do with it but I would like it to at least try to work. Im pretty sure it isnt supposed to read .280v if it reads the same voltage at the ecu with the sensor unplugged from the car. that to me is kinda broken. yeah im not getting a cel which is a miracle but i would like to see some voltage fluctuation.

Arent the secondary 02 sensors voltage supposed to fluctuate a tenth of a volt or somewhere in there?

oh yeah if it matters I am running dual 3" turbo back exhaust with no cats.

 

The FSM has the testing procedure if you really want to confirm proper operation - do you have the service manual for your car? It can be downloaded for free off one of these forums - make sure you get the right one specifically for your model (part-year update manuals also exist, e.g. 2004.5)...