Official Scangauge II Thread - Share your Data, Discuss Settings ,Problems, Findings! - Toyota Yaris Forums

enkid · 09-16-2007, 09:09 PM

Edit 9/18/07, additions/corrections

Yes, it's normal. In fact it's our DFCO indication for the Yaris. Here's why:

DFCO is by definition, an Open Loop condition, because it's a fuel cutoff. Closed loop is when the computer is using signals from various sensors to meter how much fuel to inject. At the same time, the amount of fuel injected is one of the things that creates the conditions that determine what the signals will be from those sensors. In other words, it's a closed control loop. DFCO overrides this and cuts off the fuel injectors.

If you see Open Loop any other time, except briefly after a cold start, or briefly if you're drag racing or under very heavy load like climbing a steep hill, then something is probably wrong and most likely the check engine light will come on....and a trouble code will be waiting for the scanner function of the scangauge to read.

If you were driving a manual transmission, you'd find it will also switch back to Closed Loop when the engine speed drops below about 1000RPM with it in gear and your foot is off the gas pedal. At the same time you'd feel a very slight surge of power. That's DFCO switching out to keep the motor from stalling. Then you'd quickly have to stomp on the clutch and throw it into neutral, or into low gear and go....or it'll stall anyway.

On the other hand, scangauge fuel consumption calculation is unaware of DFCO, so it registers higher consumption than if you were in neutral. In my case, this helps offs offset consumption error calculation in the other direction.

I have a 96 Chevy conversion van which sat with a dead transmission and engine problems for 2 years. I've been reviving it this summer....the SG came in really handy diagnosing....and I was surprised to find it too, has DFCO.

09-16-2007, 09:09 PM	#11
enkid Drives: 07 Yaris Sedan Join Date: Nov 2006 Location: RI, USA Posts: 25	Open Loop Edit 9/18/07, additions/corrections Yes, it's normal. In fact it's our DFCO indication for the Yaris. Here's why: DFCO is by definition, an Open Loop condition, because it's a fuel cutoff. Closed loop is when the computer is using signals from various sensors to meter how much fuel to inject. At the same time, the amount of fuel injected is one of the things that creates the conditions that determine what the signals will be from those sensors. In other words, it's a closed control loop. DFCO overrides this and cuts off the fuel injectors. If you see Open Loop any other time, except briefly after a cold start, or briefly if you're drag racing or under very heavy load like climbing a steep hill, then something is probably wrong and most likely the check engine light will come on....and a trouble code will be waiting for the scanner function of the scangauge to read. If you were driving a manual transmission, you'd find it will also switch back to Closed Loop when the engine speed drops below about 1000RPM with it in gear and your foot is off the gas pedal. At the same time you'd feel a very slight surge of power. That's DFCO switching out to keep the motor from stalling. Then you'd quickly have to stomp on the clutch and throw it into neutral, or into low gear and go....or it'll stall anyway. On the other hand, scangauge fuel consumption calculation is unaware of DFCO, so it registers higher consumption than if you were in neutral. In my case, this helps offs offset consumption error calculation in the other direction. I have a 96 Chevy conversion van which sat with a dead transmission and engine problems for 2 years. I've been reviving it this summer....the SG came in really handy diagnosing....and I was surprised to find it too, has DFCO. Last edited by enkid; 09-18-2007 at 10:21 PM.