O2s ??
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Launching!
Joined: Aug 2002
Posts: 241
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From: flordia
O2s ?? I have the diablo and it has four sets of o2s reading,I have the o2s for the rear. So which ones do i look at? The frist set or the second set? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
On The Tree
Joined: Jan 2003
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From: Central MD
Re: O2s ?? You have 4 O2 reading in Mv (millivolts), I think. Nothing really to look at unless they aren't working. You should see them jump back and forth through a bunch of numbers from low to high, then high to low. That means they are working. What you are mostly concerned with is STFT and LTFT. When you are driving at highway cruising speed for a few minutes, check them out. You should be over say 1400 rpm (55 to 65mph) to get a good reading. Your STFT should be small erratic numbers juggling between neg and pos. Your LTFT's should remain within 0.00 and neg 4.00. positive means lean and negative means rich. Anything between -4 and zero is considered satisfactory. Zero being the goal.
Thread Starter
Launching!
Joined: Aug 2002
Posts: 241
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From: flordia
Re: O2s ?? I was checking my St and Lt.
The ST were a 0.00
LT.0.00 then 5.00 then-5.00
St 0.00
LT 13.00 then -13.00 o.oo
<img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
The ST were a 0.00
LT.0.00 then 5.00 then-5.00
St 0.00
LT 13.00 then -13.00 o.oo
<img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
Re: O2s ?? Your STFTs and LTFTs are the PCMs effort at trying to keep the A/F ratio at 14.7:1. The STFTS are quick, small changes and the LTFTs are slower and bigger changes to the pulsewidth of your fuel injectors. Pos % values means the PCM is increasing the pulsewidth. Neg % value means your too rich so the PCM reduces the injector pulsewidth giving you less fuel. These values are derived from the PRE cat O2 sensors ONLY. The POST cat O2 sensor only monitor the Catalytic Converter efficiency. The PCM compares the Post cat value to the Pre cat value to see if the cat is reducing emissions. The pre cat output is supposed to look like a sine wave with a peak to peak voltage of approx. +0.1 to +0.7 vdc. The post cat value should be nearly a flat line around +0.4 vdc if the cat is doing its' job. It wouldn't look like a flat DC voltage on an oscilloscope, but it wouldn't have nearly the amplitude of the pre cat O2 sensor. Don't relate STFT and LTFT with Pre cat and Post cat sensors. STFT and LTFT is a function of the pre cat O2 sensor only. Catalytic Converter efficiency is a function of the comparision of the values of the post cat O2 sensor to the pre cat O2 sensor value.
