having a issue with a 2000 acura integra throwing itself into open loop after car fully warms up. ECT readings from live data on a obd2 scan tool showed 178 degrees at time of switch and it is a new ECT sensor. I have 2 ecu's one being obd1 and the other is the OE obd2 both are p72's. i can literally unplug the obd2 when it switches to open loop and plug in the obd1 and it stays in open loop. i have read that TPS, MAP, o2, and ECT are whats used to control closed loop but is anything else involved like IAT? Any help would be appreciated. Car runs great when its in closed loop but literally switches to open once it gets hot and sits for a minute like at a red light or drive thru. at this point im tempted to get a new wiring harness.

 

When your ECU is going into OL mode does the CEL come on at the same time? Most times when a solid CEL comes on the ECU will be put into limp mode and it switches to reading from the open loop tables.

Have you checked for any stored codes at time of the OL issue? Just a starting point as I would actually have to