The PCM relies on the Engine Coolant Temperature to make decisions, we will go over a number of them later on, here we focus on a key decision and that is when to switch from something called
Open Loop and start running is something called
Closed Loop.
Simply put when we first start our cold engines, a lot of sensors are not ready yet, for example the O2 sensors have not warmed up to their operating temperature, so they can't start reliably reporting to the PCM what the exhaust gas conditions are. The PCM has no choice but to operate in it's best guess mode, so it relies on pre existing tables, in other words Excel looking charts or spreadsheets that say something like, hey man if the coolant temperature is 70* F try to idle at 675 RPM.
Then when the Engine Coolant Temp reaches 131* F (yours may vary) the ECT sends a signal to the PCM saying, we're ready for
Closed Loop, and the system switches to
Closed Loop and the PCM starts listening to the input (in other words relying on feedback) from the two narrow band O2 sensors among other sensors. More on this later.
The nice thing is that HP Tuners allows us to monitor the Channel that shows us loop status, so lets add it next:
1. So once again either right click in the blank Channels pane and select Add Channel from the little pop up menu, or click the gray gear with the green plus + sign next to it on the top menu.
2. This will bring up a Channel Selector, so let's type Fuel System #1 Status in order to narrow down our choices, we could hunt and peck for it using the drill down method, but I find typing in what you want is quicker.
3. Then double click the Channel you want.
And now we have two channels in our Channels pane, we will now be able to see how hot our engine is, and if we are in Closed Loop yet, baby steps.