does unplugging the 02 sensor put the car into limp home mode? i want to put a wideband 02 sensor in place of the stock one so i can do some tuning before i get a new bung welded in for it. or does anyone have any better ideas on how to hook up a wideband without having a bung for it just temporarily?

 

Yes, disconnecting the O² sensor will prevent the engine from entering closed loop mode. After a time interval with no reporting from the sensor, the ECM will set an error code and enter backup fuel mode. Of course, as with every hard-and-fast rule, there are caveats. The ECM will not enter Backup Mode if the Highway Fuel & Spark Mode is invoked. In HF&S Mode, the oxygen sensor input is basically not used. However, I think it may need to at least be present since the ECM must have been in Closed Loop Mode for a period before HF&SM can be invoked. Of course, that would require an active O² sensor first.

One possible alternative is to connect an O² simulator, but this may not work with the older control systems.

 

if its unpluged will the check engine light turn on? If so mine didnt when i got the car, it ran really good till i looked over my car.

 

my service engine soon light didnt come on for about 10 minutes.
the car was running okay, a little lean while cruising and a little rich at WOT. time to weld in a bung for the wideband and get tuning.