WTF...Scanmaster is reading 000mV under WOT?!?

[Snorman]

Today, my SM starting reading 000mV under WOT. WTF? At idle, the O2's are fine, as I progressively get further into WOT, the O2's drop down to zero, with 0.0 KR (not necessarily a bad thing).
I unplugged it, and checked the plug into the ALDL (I plug in with a spade connector). I even unplugged the computer for a few minutes.
Any idea what is happening? All other expanded modes seem fine (BL, coolant temp., mph, rpm, etc.).
S.

 

[azgn]

been running any leaded fuel?

02 could be dead.....cross counts moving?

 

[Snorman]

No leaded fuel and the O2 sensor is about 2 months old. If the sensor was bad, would it read O2's at less than WOT?
What are "cross counts"?
S.

 

[Snorman]

Anyone else?
S.

 

[gofstbuick]

Originally posted by Snorman
No leaded fuel and the O2 sensor is about 2 months old. If the sensor was bad, would it read O2's at less than WOT?
What are "cross counts"?
S.

What kind of O2 sensor? Some sensor brands other than GM have had problems setting code 13 even if the sensor goes bad. Is the sensor readiings up after you mash the throttle down up? I should be. Crosscounts are the frequency at which the sensor ranges across 450mv line within the scantool refresh rate. A primative test is to introduce propane into the induction system and see if the sensor will show 850mv or better, and then pull a vacuum leak and see if the readings go below 150mv. In the b4black section, I answered a question about testing an O2 sensor, but it requires a graphing multimeter or digital storage oscilloscope. IMHO, that is the only true method of testing a O2 sensor, given current technology.

 

[azgn]

most scan tools will read cross counts...if not active, usually 02 is history

just replace it and see if the problem disappears...if not, you have a spare!

 

[kevin]

mine has the same prob.except my o2's are fine till i hit 3rd.but i also have 2 to 5 degress of knock.my fuel press. is dropping.i'm putting a hot wire on and see if that fixes it.have you checked your fuel press under wot?

 

[TurboBob]

replace the O2 sensor.

I had a Tomco O2 sensor do this exact thing.

That or the O2 sensor wire in the harness might be getting pinched at WOT or something like that.

TurboBob

 

[TurboDave]

Gotta love those Tomco O2 sensors

Had that happen to me once.

 

[Snorman]

Ahh...I've got a Tomco on the car. I bought it from Postons.
Is the general concensus that this is likely related to the O2 sensor?
S.