How can you tell which sensor is bad on a Nissan Maxima 2004 without using a scanner? Can you reset ecu by unhooking battery? I hit a tree that fell in the road in front of me, it was raining, driving away, hood flew up, shut it quickly. Now a sensor is giving me problems. Someone checked it with a scanner, but I had unplugged and plugged back in several sensors by then. I need to reset the ecu so those sensors won't come up just because I unplugged them. Can I do that by disconnecting the battery and how long will it take? Is there a way to check for codes on this model without a scanner? I tried a new mass air flow sensor, not the problem.