I have a 2009 G37 sedan with 85K miles. about two weeks ago I had left my son's house to head home ( 55 miles) I had about a 1/4 of a tank. It's mostly highway. I went about 25 miles and had a warning come up on dash 62 miles left. I thought I had plenty of gas to get to my exit ( 15 miles) within 3 miles my car started slowing down and my gauge was on empty, I was fortunate to coast to the next exit but no gas stations, gad to have someone bring me gas. I couldn't figure out what happened to the weird readings and warning I got and the gauge reading before I left. Yesterday I left with just over a 1/4 of a tank, on my way back I had just over an 1/8 of a tank. My light came on and a warning of 42 miles left. It started to count down quickly and then went to empty faster than normal. I got to the highway service station and filled up, I was surprised because it only took 14 gallons?? has anyone had an experience like this? do you think my fuel pump is on it's way out?

 

I was searching online and think I found my answer.

 

Light comes on around 3 gallons

 

I had similar issues with the gas gauge reading incorrectly on my 2011 G37 coupe. If you remove the rear seats and access panels, you can do a resistance check on the sending units with a full tank of gas (see service manual for procedure). You can also remove both sending units and clean them but you will need to make sure you have half a tank or less (it will leak otherwise) and a new set of gaskets (fuel will swell the orings and they will no longer seal a second time). I did both of these things with no luck solving my issue. After talking to the dealer they pointed me to the AC amplifier in the center stack (under the radio). This AC amp is responsible for many things but it also is used to interpret fuel level from both sending units and sends it to the speedometer. My module turned out to be bad, no way of testing it other than swapping it out. I bought on off eBay for $40 or so and have never had a problem since.

 

Mine was having issues as well, level sensor and sending unit level sensor cleaning and then replacement didn't fix it. Turned out the AC control module needed replacing, apparently that's what interprets the fuel level and communicates it to the ECU.

 

That's weird! Was it expensive? Did a local shop do it or dealer?

 

That is strange that the A/C module reads fuel level, but whatever. Were you able to replace the module yourself? I'm interested to know more about doing this if it's not too difficult or expensive.

 

If you buy the part new or ask the dealer to do it, it's several hundred $. I got mine used off eBay for $30. You have to make sure you have the correct version, they differ by vehicle manufacture date. The model number you need is written on the unit. Then it's a pretty simple swap, just take the infotament panel off and you'll see the big white plastic box. Have to remove like 6 screws or something like that. Magnetic screwdriver helps a lot. Took me 15 min to install. Do the airbag reset procedure after because when you have the panel removed, car freaks out.

And yeah, that module is responsible for communicating a lot of data, fuel level included.