2003 Land Rover Discovery 158,000 miles

If I am replacing an o2 sensor and I have the code for it and the check engine light on, and I haven't ordered my ultragauge or OBDII scanner yet can I reset the engine light by unhooking the battery for a while and the code clear out. I did it the other day and the check engine light went off for about three days then came on again. I figure thats the ecu recognizing the fault after a predetermined amount of time

 

you dont want to be doing that one of these times it may not wake back up, you can buy a cheap OBDII scanner for $30

 

Most OBD-II computers have a memory system that isn't reset by disconnecting the battery. Plus, we see many weird things happen from battery disconnects, so we try to avoid if possible. For example, we just had a 2007 Jag XK get a corrupted Car Configuration File (CCF) after the battery died and was replaced. What a nightmare to figure that one out and get it right again. Mercedes-Benz likes to fry the Signal Acquisition Modules (SAM) both front and rear at battery disconnect. Even though realistically, we are talking less than 10% of cars will experience an issue, its best to avoid disconnect if possible.

Besides, any time you replace a sensor that has anything to do with air/fuel mixture (i.e. O2 sensors, MAF sensor, etc...), we like to hook the computer up and reset the fuel adaptations. We have run into many situations that codes return because the "learned parameters" are skewed from a faulty sensor.