O2 sensors voltages way different...help

[blackshark]

Hi All,

I just ran my first scan today to find out why my '98 vette is running so rich just after it warms up. I suspected that the change in the o2 sensor configuration after my LG LT Pro headers were installed to be the culprit.

The scan showed bank 1 all blue and bank 2 almost always white. One averaged 948ma and the other was 56ma.

In addition I read the DTCs and two error popped up:

p0152 h02s circuit high voltage bank 2 sensor 1
p0171 fuel trim system lean bank 1

The DIC threw out a Charge System fault just for fun too.

Any ideas on the cause or solutions? ???

Thanks,
Jay

[jimmyblue]

I think I'd start in reverse order, nothing is very
trustworthy if the power is flickering.

That O2 discrepancy is very abnormal. However
I would look more at the dynamic activity (or lack)
in closed loop idle / cruise to see the health of the
O2 sensors.

Here is a picture (superimposed from two very different
vehicles) of O2 behavior. The upper is long tubes and
the lower, my car with stock manifolds. The upper is
barely alive, mine switches very wide and fast. Being
stuck low most of the time makes the closed loop try
and trim it back up (even though the actual mixture
may rich or lean, the sensor just sits there low).

Of course dead railed is another matter entirely and
stuck-high is an abnormal failure mode (but one that
might result, for example, from burning off the insulation
so heater can short or merely leak into signal, etc.).

[blackshark]

Thanks Jimmy,

What chart did you use to look at those 02 readings?

[jimmyblue]

Just the standard "trace" display that comes up when you
hit the squiggly-lines icon on the logger in playback.

I cropped / cut / pasted the strips from the two vehicles
into one .gif, just for "illustration purposes".

[blackshark]

OK Jimmy....here is the screen shot of my log...looks like my B1S1 is one of the 'sleepy' types.

Would you just replace it or look for some type of grounding/melting in the upstream line or both?

[WS6snake-eater]

I would ck for melted wires, or loose ones, if they used extensions.

[blackshark]

OK....here is my screen shot. What do you think?

http://www.geocities.com/boomstick_4_u/o2.jpg

I will let you know what we find when we get it back on the rack.

Jay

[jimmyblue]

Bank1 O2 sensor I think is just dead, shorted to ground or
open circuit. You show a high positive trim, high injector PW
and no sign of fuel. Meanwhile the B2 is the opposite, though
it at least shows some signs of life.

No chance you've got the injector drive harnesses reversed,
bankwise, is there? ???

[blackshark]

You think B1 is dead? I thought the high voltage on B2 indicated a ground???

It is possible the sensors are reversed. I will know more when I get it on a rack.

[blackshark]

Problem solved....mostly. It looks like the O2 sensors were reversed from left to right. I unplugged one and the other controlled both injectors just fine( it set the dead sensor to 447ma...right in the middle). When I switched the sensors lines, both sides operated just fine, although, the B1 sensor is a little slower than B2.

Thanks for the help guys!!