How to force OPEN LOOP mode on OE ECU??

[maxthehax]

Hi guys! I dont know if Yaris ECU would work the same on this topic but lets try...

I don't think its a surprise if I say that toyota ecu are complicated...

I run on a FI/c, the car was tuned on a ''acceptable'' level, by modifying the volts sent to the O2 while closed loop. Everything was fine for a while...

Someday, I step in my car, go for the routine drive and bang 17:1++ air/fuel, I was barely able to cruise and accell... tried reseting the ECU by unplugin battery for 10mins, still the same...

hookin up the laptop to the fi/c , nothin has changed execept I saw 0volts on both O2, just like 02 were not working anymore so I had to add some fuel in the fuel map to get richer... weird

now I am about to retune the car to get something acceptable on open loop with only the fuel map. I dont want to do so and bang O2 starts to work again lol :P

So here is my question, is there a way to make sure the OE ecu go automatically in open loop??

Unpluging the OE O2 sensors?
If FI/c is in voltage mode for O2 and I put 0 everywhere?? I think that idea doesnt work...

Thanks for your help!

[YarisSedan]

If by open loop you mean when the computer is not looking at your o2 sensors and not in control of the fuel trim you could probably simple disconnect your engine coolant temp sensor to manually keep it in open loop. The ECU dosnt go into open loop till i think it measures thermostat open at 180 degrees or so. Not sure what the yaris reads when the ect signal is loss some cars it will just show hot and turn the cooling fan on all the time. If that dosnt work I would just buy a cheap ect sensor and just have it plugged into the connector sitting there while leaving the factory one installed in the car. It will read then the ambiant air temperature keep the cecl off and fool the computer it will keep it in open loop indefinitely until you plug it back into the stock one.

[maxthehax]

Originally Posted by YarisSedan

If by open loop you mean when the computer is not looking at your o2 sensors and not in control of the fuel trim you could probably simple disconnect your engine coolant temp sensor to manually keep it in open loop. The ECU dosnt go into open loop till i think it measures thermostat open at 180 degrees or so. Not sure what the yaris reads when the ect signal is loss some cars it will just show hot and turn the cooling fan on all the time. If that dosnt work I would just buy a cheap ect sensor and just have it plugged into the connector sitting there while leaving the factory one installed in the car. It will read then the ambiant air temperature keep the cecl off and fool the computer it will keep it in open loop indefinitely until you plug it back into the stock one.

Yes. By open loop I mean when there is no O2 reading.

I have a scangauge, I can see open/closed status, and I dont think it is always directly connected to the temperature readings. When the car starts at cold it's open loop by the time O2 gets hot, and I can see the closed loop arrive way before my car gets the 185 degree mark (85 celcius, operating temp).

...if by exemple the main O2 stop working for any reason, it should send no signals to the ECM (0 volts), WOULD'NT THAT FORCE THE ECM TO RUN OPEN LOOP?? Because I think this is what I experienced, but I dont know what caused the O2 to send no signals.

What I know is while the O2 sent no signal, I was running way too lean where normally I was perfectly fine. I were able to correct that by adding fuel in the map, where normally it changed nothing because the O2 was the main controller.

I think is it pretty hard to explain for me, but my main question is about how to get the car running permanently on open loop, so I can easely tune it without messing with the O2 again. Maybe you are right about unpluging the coolant temp sensor, but I doubt about it, maybe some1 else could chime in?

[maxthehax]

After couples research...;
I think you are right about the temp sensor. Unpluging it would force the ecm to open loop because he should never know when the engine get a minimum of warming...

The problem it creates is, I use scangauge to monitor my Coolant temp, without sensor plug'd in its imposible to read. I will need to add another gauge to read temp for peace of mind. I do know that my engine Never overheated, coolant system as always worked perfectly fine and steady...

...; I have a AEM digital oil temp gauge. Is it possible to use that as a water reader? I think the answer is yes, if I remember right because the only difference should be the front printed facing showing OIL instead of WATER. ??

Thanks so much for helps!

[YarisSedan]

Well closed loops dosnt necessarily start at 185 could be our car starts a little earlier than that when the thermostat barely starts to open. Typically takes about 4-6 minutes from the time the vehicle is started while your driving. If the vehicle is seen running cold the vehicle will never go into closed loop and will constantly run excessively rich. Watch what happens to your fuel trims when you disconnect your ect sensor.

[maxthehax]

Originally Posted by YarisSedan

Well closed loops dosnt necessarily start at 185 could be our car starts a little earlier than that when the thermostat barely starts to open. Typically takes about 4-6 minutes from the time the vehicle is started while your driving. If the vehicle is seen running cold the vehicle will never go into closed loop and will constantly run excessively rich. Watch what happens to your fuel trims when you disconnect your ect sensor.

I just hope to be able to cheats values easely :P

thanks for your help.

I will let know how it was with the aem fi/c...

This is a temporary use of it, I am completely decide to go with EMS when I will have time/space to do my engine swap.