What is the average Scangauge II offset percentage ? - Toyota Yaris Forums

sbergman27 · 03-05-2010, 09:08 PM

I'd like to present my understanding of how the cutoff feature works and get corrections and feedback if I'm off.

The scangaugeII uses the open-loop condition to recognize DFCO. However, there are 4 conditions which can cause open-loop operation on the Yaris, and FI systems, in general:

1. Engine cold.
2. Wide open throttle.
3. Diagnostic failure (bad sensor, broken wire, etc.)
4. DFCO.

The ScangaugeII cutoff feature no doubt ignores the open-loop when the engine is below a set temperature or when a diagnostic failure is detected. However, different cars have different scales wrt the TPS. My 2008 Yaris ranges from 16 at idle to 80 at WOT. The cutoff is simply the value above which to ignore open-loop for the purposes of detecting DFCO. So... it doesn't have to be precise.

I've heard people say that the default value (24?) gave them 9999 when they didn't think the engine could be doing DFCO. But I don't understand that. How could a warm engine with no diagnostic problems be in open-loop mode at anything near the default cutoff value?

I do find that I need to set mine to the idle value + 1 to get a 9999 reading. Apparently, the TPS must be < and not just <= the cutof value for it to work. But there should be no functional difference between 17 and 24. In fact, any value up to the point where the engine goes open-loop for WOT mode should be equivalent to 17. Either the engine is in open-loop and doing DFCO or it is not, regardless of the TPS as long as it is below the open-loop point for WOT. (Which I imagine is actually less than 80.)

-Steve

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03-05-2010, 09:08 PM	#1
sbergman27 Drives: 2008 Yaris Sedan Join Date: Feb 2010 Location: Oklahoma City, OK Posts: 323	I'd like to present my understanding of how the cutoff feature works and get corrections and feedback if I'm off. The scangaugeII uses the open-loop condition to recognize DFCO. However, there are 4 conditions which can cause open-loop operation on the Yaris, and FI systems, in general: 1. Engine cold. 2. Wide open throttle. 3. Diagnostic failure (bad sensor, broken wire, etc.) 4. DFCO. The ScangaugeII cutoff feature no doubt ignores the open-loop when the engine is below a set temperature or when a diagnostic failure is detected. However, different cars have different scales wrt the TPS. My 2008 Yaris ranges from 16 at idle to 80 at WOT. The cutoff is simply the value above which to ignore open-loop for the purposes of detecting DFCO. So... it doesn't have to be precise. I've heard people say that the default value (24?) gave them 9999 when they didn't think the engine could be doing DFCO. But I don't understand that. How could a warm engine with no diagnostic problems be in open-loop mode at anything near the default cutoff value? I do find that I need to set mine to the idle value + 1 to get a 9999 reading. Apparently, the TPS must be < and not just <= the cutof value for it to work. But there should be no functional difference between 17 and 24. In fact, any value up to the point where the engine goes open-loop for WOT mode should be equivalent to 17. Either the engine is in open-loop and doing DFCO or it is not, regardless of the TPS as long as it is below the open-loop point for WOT. (Which I imagine is actually less than 80.) -Steve