Open Loop/Closed Loop.

[JockoT]

I was aware that DFCO doesn't come into effect until the engine is sufficiently warmed up and thought it was a function of the Open Loop/Closed Loop. This morning I set the ScanGauge up to show me Coolant Temperature and Loop ststus, with a view to finding out at what temperature the changeover occurred, but almost from the get go the system was cycling between Open and Closed Loop. This happened even before Blue dashboard Engine Temp light went out.
I take it there is more in play than I first though?

[Stacygifford]

From what I have had the opportunity to observe, newer cars are going into Close loop sooner and sooner.
Basically, if coolant temp is above 105°F. (just a rule of thumb, it varies from car to car.) or the Oxygen sensor has varying output voltage (indicating it is hot enough to operate properly). they will go to closed loop

If it is on your Honda Jazz, I think that they have an integrated exhaust manifold (cast into the cylinder head) If that is the case, they can warm up quite quickly.

How warm was it outside when you tested this?

[JockoT]

Thanks for the quick reply. My Jazz is a 2006, so it has a separate exhaust manifold. Outside temperature this morning was about 18°/65°F.

[Stacygifford]

Your thread got me to thinking .On my way to work this morning I decided to watch my wideband gauge. On my Honda even immediately after start up It seems to feel cut under deceleration.

The car was still in open loop though .I know this because my 02 sensor is programmed to run at 16 to 1 as opposed to 14.7

I was idling at 14.4 to 1 and under load at around 13.8

But as Soon as I let off the gas, The gauge pegged at 22.4 to 1. It may not have been completely cutting Fuel but it was definitely at-least leaning it out .

It appeares that it only took my car about 40-50 seconds to go in to closeed loop mode. This morning 71°.

There is a chance that the 02 sensor I installed warms up faster than the factory one and that could play a role in that though...

[JockoT]

Further checking on my part showed that the O2 sensors are heated so that could explain the quick warm up. However, the car doesn't operate in DFCO mode until the coolant temperature reaches 60°C. Perhaps that signal is used along with the closed loop signal.