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+--- Thread: OBD2 Reading: Closed Loop vs Open Loop (/thread-obd2-reading-closed-loop-vs-open-loop)
OBD2 Reading: Closed Loop vs Open Loop - sina27 - 08-24-2022
Hey guys
I got a 1996 Geo Tracker 2WD, 5 speed, 16 valve MFI.
I just recently did a bunch of tune ups and replaced 02 sensors, TPS calibration, etc. Car is running good and idling fine.
No check engine light.
I plugged in my OBD2 scanner.
The car reaches proper operating temp during idle and while driving (~194F).
After start up and when warm, the car is in CLOSED LOOP mode during IDLE. This is expected.
While I'm driving the car, the car is also in CLOSED LOOP for most of the time.
HOWEVER - while I'm driving / accelerating, if I let go of the throttle and coast, the scanner switches to OPEN LOOP for 5 seconds or so, before going back to CLOSED LOOP.
It seems to hit closed loop intermiddently, only when I'm driving above a certain speed and when I lift my food off the gas -
So say I'm driving 50mpg and giving it gas, its in CL, and if I suddenly give it no gas and coast while in gear, it switches to OL for 5 seconds before going back to CL.
The ECT stays above 190F the entire time so its not a temp issue.
Is this normal? My front 02 sensor is reading correctly. I noticed that the front 02 sensor slams low voltage when I take my foot off the gas while coasting (when it switches to OL).
And then once the front 02 starts bouncing again like normal is switches back to CL.
Is this normal or is something wrong?
RE: OBD2 Reading: Closed Loop vs Open Loop - fixkick - 10-29-2022
when you lift right foot fast moving fast in or out of gear
the ecu goes to cut fuel mode. (and even plays games with EGR to cut human neck snapping ,pain?)
there is no fuel so there can be no, FUEL TRIM with no fuel nor can it do closed loop in cut fuel mode. nor in WOT.
there is one more trick in play the ecu wants to keep the cat hot at all times. so will burn fuel at odd times,
the cat must be kept hot and does waste fuel to do that and may go CL , in cut fuel mode but really is not, cut fuel, so may cycle in that mode
out of gear it is just idle mode so would be in CL.
CL is always O2 swinging this is ECU trimming fuel fast about 6 times a second rate. ( and during the trim the 02 jogs to waste fuel just for the cat keep hot rules)
the 02 jog is caused by injecting rates joggng a tad..all done by ECU on purpose.
the jog rate will be by the slowest thing in the trim,, ecu processing time or injector delay or o2 speed, or all 3.
yes ECU are strange beasts and thanks for sharing such and interesting topic.
good luck and hide from Ghosts soon.