Can someone who is familiar with these (or has a Durametric) tell me what their pre cat O2 voltage is reading? Mine are reading a steady 1.5V on both banks. From what I understand, they should be reading about 0.7V and fluctuating. I'd like to confirm that both my pre cat O2 sensors are bad before I buy new ones. Could something else cause these readings? I did a leak test and everything seems tight.

 

Are you sure you actually observing the #1 sensors? Unless you have a pretty sophisticated OBD2 code reader/data viewer it probably won't be able to read/view the #1 sensor voltages. These are wide band (aka broad band) sensors and the PID to read them is a higher PID than the 1st 32 PIDs most generic OBD2 tools support.

For example my Actron OBD2 tool can't read the pre-converter O2 sensors because they are not within the 1st 32 OBD2 PIDs.

All I can observe are the post-converter O2 sensor readings.

Even though the Turbo #1 sensors are wide band I believe the #1 sensor voltages should be swinging up and down as the DME switches from a slightly rich fueling to a slightly lean fueling at about once a second (at idle).

My reference indicates the wide band sensor voltage range should be between 0.7V and 4.0V.


Hold everything!

Curious I did some research and the wide band sensor is able to measure from around 10:1 to 20:1 where the narrow band was centered around 14.7:1. While one could know the mixture was leaner or richer one didn't know by how much so the goal was to keep the mixture confined to just either side of 14.7:1.

With a wide band sensor one can know how much the mixture differs from ideal or stoichiometric.

The reading then should not swing up and down but remain stable, with if I understand correct with a reading of 0.45V which indicates a stoichiometric mixture.

A reading of 1.5V suggests then an absence of oxygen thus an overly rich mixture.

And there's more. To save me from having to type this in I just cut/pasted it from a Bosch document:

The wideband oxygen sensor receives a reference
voltage from the engine computer and generates a
signal current that varies according to the fuel
mixture.

When the air/fuel mixture is perfectly balanced at
14.7:1 (the stoichiometric ratio and lambda equals
2), the sensor produces no output current. When the
air/fuel mixture is rich, the sensor produces a
"negative" current that goes from zero to about 2.0
milliamps when lambda is 0.7 and the air/fuel ratio is
near 11:1.
When the air/fuel mixture is lean, the sensor
produces a "positive" current that goes from zero up
to 1.5 milliamps as the mixture becomes almost air.

Here's the link:

http://tayloredge.com/reference/Scie...gensensor3.pdf

Based on the above then a 1.5V reading indicates not a rich condition (in the sense of too much fuel) but "rich" in the sense of rich in oxygen content condition. Thus the 1.5V reading suggests an air leak or a fuel supply/pressure problem.

Confused? I know I am...

 

Confused? Yeah, no kidding.
I'm using the Durametric cable and software which reads out the pre and post O2 in voltage. It's a good diagnostic tool, now I just need to figure out what the information is telling me.

 

want a hot idle reading Jean-Marc?

 

Yes please

 

Me too.

 

~1.45-1.5V at 750rpm, MAF @ ~19kg/hr

 

Ok, that's the voltage I'm getting. My rpm and air are a bit higher but that's probably not an issue.
One more favor, post cat?

 

I'll try to grab one tomorrow, I can send a log as well if that helps... maybe msg/email me a reminder tomorrow
Cheers,