Scanmaster o2 milivolts bouncing back and fourth

[griz_83ho]

As stated above I installed my scanmaster 2.1 and the o2 milivolts reading will steadily get to 820 to 840 after initially starting and hold there but a soon as you give it gas it will bein bouncing to 200, 050, 450, 825, back to 200. There is no sequence just jumps all around. And the mph reading is off as well. It is reading almost half of my actual speed. Those are the only two that look off. I wired it into the Aldi plug under the dash but pulling a hot wire, ground wire from there. Is that the problem?

 

[Sydwyndr]

The SM should hook in to the top of the ALDL 2nd pin over from the right. The random O2 bounce is completely normal as this is showing you that the O2 is responsive like it should be. If you see like 453, 502, 516, 486, etc.... then the O2 has stopped and needs to be replaced. Depending on the chip that you run if its a open loop chip it may show high 700s low 800s at idle but should return to normal as you pull away.... As far as the MPH being off I cant answer that...

 

[DavzGN]

Do you have a 145mph speedometer? If you do, it probably has a reducer which will make the computer read wrong.

Posted from the TurboBuick.Com mobile app

 

[griz_83ho]

Damn your good, good call that's why the mph is off then. As far as the o2 milivolts bouncing all around then it would be caused by a bad o2 sensor? Like I said on initial start up it holds 840 to 850 but as soon as you accelerate it goes all over the place and never registers any knock. Never settles back to consistent 800 unless shut off and started later

 

[StageII86]

No, it is a narrow-band O2, so it oscillates from a higher to lower voltage and the computer finds the stoich AFR from averaging along the "narrow band". The Scanmaster is slow so you just see numbers bouncing around that's totally normal. You should see something like a 0-200 range number, then a 6-900 range number, back and forth (but nit always - just depends on what frames the SM is catching). At WOT the car goes rich so the voltage maintains a higher number (750-820 considered ideal for many). if you have a bad sensor, the switching gets very lazy or just stops and the voltage reads between like 400 and 600 all the time with no big swings either way.