My 2007 Infiniti G35X Sedan's check engine light came on. I used my cheap OBD 2 scan tool to scan the car's engine computer for codes. The codes were P0031, P0130, and P1148. These codes all point to a faulty Bank 1(Passenger Side) Heated Air/Fuel Sensor. This is the sensor before the catalytic converter, not after. Specifically, it looks like the heating element in the sensor had died or shorted out internally. The heating element in the sensor heats the sensor to be able to read oxygen/fuel content in the exhaust and send this information to the car's computer for fuel adjustments. Using my OBD 2 scan tool, I scrolled to the Live Data menu and looked for the bank 1 A/F sensor(02B1S1 in the live data). With the engine running and hot, I found that the sensor's value was stuck at a constant voltage of 2.250V when revving the engine. I compared this to the driver side, bank 2 sensor, in the Live Data menu(O2B2S1) and noted that while revving, the sensor's voltage would change between roughly 2.2V and 2.4V. This told me that the passenger side sensor was in fact dead as it's voltage didn't fluctuate and was stuck. I decided to remove the sensor and measure it's resistance as a last step in confirming the diagnosis. To do this, I removed the passenger side intake hose and intake box by loosening the hose clamp on each end of the intake hose, disconnecting the Mass Airflow Sensor connector on the intake box, disconnecting the PCV hose(1" diameter hose) from the intake hose and removing one 10mm bolt from the intake box. From here, you can wiggle the intake hose off of the throttle body or the intake box. Once the hose is off, you can simply pull up forcefully on the intake box and it will come out.This gives you access to remove the A/F sensor. The sensor sits in the exhaust, right after the point where the exhaust manifold and downpipe meet, towards the rear of the engine. To remove it, you will need and Oxygen Sensor removal tool, a ratchet or an impact gun, a universal joint to put on the Oxygen Sensor Socket and a variety of socket extensions. Soaking the sensor in penetrating oil for several hours or a day before can help here. Disconnect the sensors connector from the engine wiring harness connector, install the O2 tool on the sensor, put a universal joint on the end of the socket and then put a variety of extensions on until the last one peaks towards the top and gives you access to put a ratchet on or an impact gun on. Turn the ratchet or impact gun counter clockwise while making sure the socket stays on the sensor. The sensor should begin to unscrew.Once removed, you can test the internal resistance of pins 3 and 4 of the sensor. According the the Infiniti Factory Repair manual, the resistance between pins 3 and 4 of the connector should be between 1.8 and 2.44 ohms while at ambient temp(77 degrees F). My resistance between these pins was greater than 25,000 ohms, indicating that the element was bad. I replaced the sensor with this part, Denso 234-9072, reinstalled everything in the reverse order and then started the engine. With my cheap scan tool plugged in to the OBD 2 port, I selected Live Data again and went to O2B1S1 and now saw the voltage was fluctuating appropriately while revving the engine and was no longer stuck at one value.Repair complete. I cleared the code and test drove the car. Everything was well. It's worth noting that the factory sensor from Infiniti is in fact a Denso sensor. This is the exhaust same sensor, just without the Infiniti/Nissan part number on it. DO NOT TRY TO SAVE MONEY AND BUY AN OFF BRAND SENSOR. You are inviting a potential headache into your life. Off brand sensors can work, but sometimes they don't work or react differently than the factory sensor. This could lead you to question your repair or start looking at and replacing other things because you believe that the sensor was not the problem when in fact it is and the knock-off sensor didn't fix it. Why introduce a new unknown variable in to your repair. Also, if you have these codes, this is not a guaranteed fix for your problem. Take the advice here with a grain of salt, learn how to diagnose properly/measure resistance/view live data and interpret the results. These codes usually indicate a faulty sensor though.