The O2 sensor reading -26%

[motolink]

While I have been trying to work out why I can't get the TPS green light to come back on I noticed on the diagnostic screen the O2 sensor reading -26%, have not taken any notice before but is this ok?

Also on the same screen I have the O2 box ticked, is that correct with the PCV and AT connected.

 

[dougl]

While I have been trying to work out why I can't get the TPS green light to come back on I noticed on the diagnostic screen the O2 sensor reading -26%, have not taken any notice before but is this ok?

Also on the same screen I have the O2 box ticked, is that correct with the PCV and AT connected.

No. The PCV is controlling the fuel based on the wide band sensor. You don't want the ECU looking for an O2 signal, so uncheck it. Don't you have a Dynojet O2 controller plugged into the O2 sensor connection to the ECU? These should come with all Power Commanders. This doodad fools the ECU to not look for an O2 signal, the same as unchecking the O2 box does.

 

[motolink]

Yes I do have PCV O2 sensor fitted, but I should still uncheck the O2 box on the tune ecu screen, right.

 

[dougl]

Yes I do have PCV O2 sensor fitted, but I should still uncheck the O2 box on the tune ecu screen, right.

My question was do you have the little white plastic component that Dynojet calls the "O2 controller" plugged into the cable connector the comes from the ECU and is plugged into the cable coming from the stock O2 sensor? Didn't you remove the stock O2 sensor to install the wide band? The other side of that connection (going to the ECU) can't be hanging there if the O2 box is checked.

 

[Claviger]

I tried o2 sensor enabled using the dynojet white sensor eliminator, CEL came up instantly. Just disable it in the ecu and keep the chance of a CEL from existing.

Trims in the ECU: Disable the O2 sensor ( unchecked the box) then do a " reset adaptive". Thrn, retune with the PCV auto tune, it keeps the ecu from applying fubar adjustments and allows your tuning to be consistent.

 

[HansO]

Leave it Checked as that is why the Eliminator is there to tell the ECU all is good and having a -26 will happen from time to time nothing to stress about

 

[dougl]

I was wondering if his stock O2 sensor was still connected. If it is and the box is checked, there will be a big conflict with the pcv-at. If it is not and there is a dynojet o2 controller plug, it shouldn't matter if the box is checked, but I would uncheck it anyway. If the o2 controller plug isn't there, the box should be unchecked.

 

[TURBO200R4]

well this is getting good. what does the directions say?
i guess it depends on what is hooked up to the o2 connector.
i don't know $hit about those aftermarket boxes that why i am giving my opinion
if it uses a wide band o2 then i think it would take that info and program it to a voltage that the ecu can use and put it back into the o2 connector and u would have to have the o2 checked for the ecu to get the wide band o2 info.
if u have the bypass i would assume that gives a fixed signal and u would have to have the o2 box checked other wise if unchecked the ecu would set its own voltage.
i guess i have thought enough for one morning.

 

[Paul Bryant]

i don't know $hit about those aftermarket boxes that why i am giving my opinion

i guess i have thought enough for one morning.

I like the way you think

 

[dougl]

well this is getting good. what does the directions say?
i guess it depends on what is hooked up to the o2 connector.
i don't know $hit about those aftermarket boxes that why i am giving my opinion
if it uses a wide band o2 then i think it would take that info and program it to a voltage that the ecu can use and put it back into the o2 connector and u would have to have the o2 checked for the ecu to get the wide band o2 info.
if u have the bypass i would assume that gives a fixed signal and u would have to have the o2 box checked other wise if unchecked the ecu would set its own voltage.
i guess i have thought enough for one morning.

The wide band O2 sensor that is used by auto tune with the PCV is, as far as I know, completely independent of the ECU. The PCV intercepts fuel pulses from the ECU and uses the auto tuning function to modify those pulses. For a stock setup, the ECU uses the stock narrow band sensor to determine the fuel below about 20% throttle and below about 4400 rpm. You can prevent it from doing this by unchecking the O2 box, as virtually all custom tunes do.

The PCV should be getting a constant pulse from the ECU for every TP and RPM. When the ECU is in closed loop, using the narrow band sensor, it isn't clear how consistent the pulses are for a given TP-RPM pair. So, the auto tune may or may not be able to adapt in a reproducible way.

Better to get rid of closed loop operation altogether and either plug the narrow band sensor connection with the Dynojet part or uncheck the O2 box in TuneECU or do both.