I cna't complain i have driven this car for a year with no problems. recently the CEL came on for the knock sensor and front o2 sensor. Both were replaced Saturday. Then on my way home from work (half asleep) i see the light come on. (0706) i looked in the stickies and it came up undefined. help would be greatly appreciated.

 

Not questioning your abilities, but doesn't look like 0706 is a valid code, so possibly a miscount on blinks? I know I have had to watch is cycle a few times to make sure I got it right. Since you mentioned you already had to replace it, I would say you're looking at the following: 0707
Your Maxima engine is OBD-2 compliant. All Diagnostic Trouble Codes are four digits, with the first is always 0 or 1. Therefore your "77" is actually "0707" which points to the rear Oxygen Sensor.

Your Maxima has three Oxygen Sensors. Two are front sensors, mounted in
the Y-pipe between the exhaust manifolds and the Catalytic Converter. One
is a rear sensor, mounted in the exhaust pipe downstream of the Cat.

When both front Oxygen Sensors are operating normally the rear sensor serves only to keep tabs on the Catalytic Converter. That's the reason your engine is running well. The Engine Control Module (the computer) is not using the signal from the rear sensor to control engine management functions.

Thanks to the ECU sticky

 

i could have mis counted it was late at night and i was not to happy to see the light come back on. i will check when i get home from school and let you know. thanks for the response.

 

i checked it this moring like 3 times 7 long and 6 short blinks. I reset it and drove like 50 miles today it's still off.