Does the car give some clue when it shifts from Open Loop to Closed Loop? That is, some way the driver could definitively tell when that happens? On our old Protege5 I could tell by a change in the idle, but that only works if the car is sitting still, it would be nice to have this information when the car is moving. Failing that, any idea which of the huge number of displays available in Torque Pro (with the Prius PIDs added) will show this? I'm curious because the car seems to be slow to warm up, as judged solely by the change in MPG on the bar display. Might or might not be correlated with the OL to CL transition. Seems like it should be.
Generic OBD2 data should have a PID such as "loop status" (OL or CL, open or closed, etc). Or look to see when STFT starts moving around. As far as actually "warming up", you can monitor ECT (engine coolant temperature) to see if the thermostat is working correctly. Most failures I see are the stat opening early. If it gets real bad then the ECM should set P0128, but that's "should". You can check ECT on an extended 50-60mph cruise (ICE running continuously)on a cold day (turn heater off) - ECT should stay around 180°F. Airflow should remove heat faster than the ICE can supply it. Or start the (cold) engine and monitor ECT while keeping throttle applied in park so that ICE stays running. ECT should fluctuate after CHS operation then climb steadily, before "leveling off" around 180°F. Once the radiator is fully "hot", then ECT will go up again. Before the stat opens, the radiator core should stay cold. Posted via the PriusChat mobile app.
Used Torque on the return trip. Got on the highway and drove along occasionally checking coolant temperature and closed/open. It was 65F outside, driving around 65-70 mph, and it took almost 15 minutes before it went to closed loop. Coolant temperature hung for quite a while around 181F but then finally got up to 185F, at which point it went to closed loop. When the car turned off the highway after about 35 minutes, and had to wait 30s on the off ramp it fell rapidly to 180ish and went to open loop. After that on the rest of the trip after a short rest stop (15 minutes) it would quickly get back up to 185F and go into closed loop, like in a minute or two, not slowly like at the start. This even though the ambient temperature in the central valley was cooler, at around 50F. The car only went over 185F when going up a steep sustained slope. The highest I saw was 192F. It might have gone higher going up the grapevine, but I couldn't take my eyes off the road there to check, as there was too much traffic. Sitting on I5 cruising along at 71 mph, it was like the coolant temperature was nailed at 185F. I bet the slow initial warm up was because the car had sat for a week in an unheated garage (mean temp, not sure, 45F?) without being driven, and had only been driven 5 miles (two short trips of 2.5 miles) the previous day. The thermos tank was likely full of cold coolant at the start.
