Nissan vehicles require accessing the factory ECU. These ECUs can be placed in five different types of diagnostic modes. For checking trouble codes, the ECU needs to be put into Mode II (Self-diagnostic results). The ECU contains a dial (potentiometer) on the side of the case. This can be accessed by unbolting the ECU, making sure the factory wiring harness is still connected. Place the vehicle in the "ON" position and turn the dial fully clockwise with a flat head screwdriver, wait 2 seconds, then turn the dial back fully counter clockwise. At this time, the check engine light should reveal the vehicle's status. Some of the ECUs will also contain a red LED that will also give flash sequences just like the check engine light. If your Nissan has a green and red LED, the sequences will read as green for digits of 10 and red for digits of one.