a/f meter signal too low,what may happened

[fct]

My friend who own a mitsu engine with its O2 sensor connect to apexi timer get a very low reading on O2 voltage,0.07 to 0.18volt only.last time it was fine can get normal reading.
sensor already change to another unit but still the same scenario.
the O2 sensor is a 2 wire unit.(blue/white)
i measure the voltage direct from the sensor both wire and get 0.1v same as what shown in the timer.Then i measure with a multimeter,the signal wire (+)and the chasis(-) ground then i get 0.45v.
conclusion,is it the sensor earth no good?
where does this sensor earth wire(black) go,to the ecu unit earth?
i did try to earth the sensor ground wire to chasis but still the same low reading.

need urs opinion to settle this problem as the ecu read always lean.

 

[YuHaNiSa]

earth goes to - bat.

 

[SkYwAlKeR]

any possibility ur engine AFR running lean??...

http://img37.picoodle.com/img/img37/4/4/22/f_narrowbandom_e7a5e0e.jpg

 

[BananaBoyz]

if your air fuel ratio to lean..piston will crack,valve crack or mabey worst your engine block got hole

 

[boyzone]

Did u check on the spark plug?
Is the spark plug show that u are running lean?

 

[ihsan000]

try grounding and reset ur ecu, or try change the o2 sensor

 

[boyzone]

check on the spark plug first before do anything.

 

[fct]

prob solve,thanks.
the sensor wire ground not correct connect by the a/f meter.
reconnect then ok.
FYI,done with wideband tuning but the apexi timer read low reading that time.