2006 infinite m35x has fault code po463 and po183 and my gas guage stays on empty most of the time but not always. no other codes but my display for tire pressure has all x`s instead of the pressure.

 

Unplug the fuel pump harness, use a digital multimeter and read resistance across pins 2 and 5, it should scale in resistance from 3 to 80 ohms depending on fuel level from full to empty. I'm fairly sure it's the same process for the M35 as the G35 since so many other components are interchangeable. You should also be able to put your instrument cluster in diagnostic mode by holding the trip odometer button while you turn the key to ON then press the trip button 3 times quickly. Once in diagnostic mode you HOLD the trip button to make every needle gauge rise 25%.

If the fuel pump is sending what looks to be the correct resistance reading (should be 80 ohms on a full tank) then the problem is likely the instrument cluster. If the fuel pump is NOT sending the correct resistance (I suspect the failed value would be zero to 3 ohms or so) then the problem lies inside the fuel tank. You may be able to clean the contact points on the float, they wear out over time but can be "beaten back into shape" carefully so the metal contacts are touching again, you'll see what I mean if you have to pull the pump out.

Here's what the fuel pump harness looks like so you can find pins 2 and 5.

 

You do NOT pull the pump for the pin 2 to 5 resistance check, it's all done with the pump installed, just unplug the harness and measure those pins on the PUMP on the harness back to the combination meter.

 

So my gauge has been doing the always reads half tank when empty thing for a while now and I've finally gotten tired of being stressed about setting/watching the odometer for fuel level. I've read through the thread and measured both my sensors. With a close to empty tank (i filled with 17.5 gal after this test) I measured 37ohm on the fuel pump side and 40ohm on the driver side with the sensors installed. I pulled them both out to measure the resistance over the range of travel and confirmed 3ohm on both when the lever is at the top stop. The pump side measures 80ohm at the empty stop and the driver side measures 40ohm at the empty stop. These measures seem to match what is described in this thread as normal. What I find unusual is how non-linear that last gallon or two must be for the pump side and if that's normal. Does this seem right?

I guess I'll pull the cluster and check the resistors....

 

change the AMPLIFIER CONTROL AIR CONDITIONER 277601NM6D and it resolved my problem.