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Discussion Starter #1
MIL keeps coming on for P1464 - Fuel Level Sensor Circuit. There are specific codes which elaborate on low/high voltages, this one is just for the circuit. Some Googling reveals that a bad part results in fuel guage always showing overfilled or below empty, but my fuel gauge is working normally, so this is a contradiction. Not really sure I want to drop the tank and replace it when it's clearly working. Anyone run into this false positive issue in the past? I can't get inspected until corrected.
 

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Any time I've run into this code, it's always been due to a faulty fuel sending unit. There were some corrosion issues that occurred within the top part of the sending unit and there was a recall. You should check to see if there's an open recall for your sending unit. If so, Nissan will still replace it for free. I had mine done on my 2003 just last year, as well as a recall for the lower steering shaft.
 

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Discussion Starter #3
About 3 hours ago I was in the engine and noticed a slight hissing sound coming from behind the intake manifold. Turned out to be a crack in the hose going from the Fuel Pressure Regulator to the intake tube on the manifold. Now I'm not saying this is conclusive or anything, but this is the first time I've stopped receiving the Fuel Level Sensor code. As I stated in the description, my fuel gauge is working fine, the code made no sense to begin with. Fingers crossed.


On a separate note, I did learn today that Nissan did in fact have a recall on the Fuel Level Sensor. I thought statue of limitations had run out, but if you just got one replaced then I'll
definitely look into it if the code resurfaces.
 

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Discussion Starter #5
Anyone got a bead on the wiring location for the fuel level sensor? I'm confident that the part is fine. I'm thinking the issue occurred when I retapped the harness. Problem is I had the entire dash out as well, so without knowing exactly where the wiring is I'd need to rip everything apart and redo it. Not fun ?
 

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You test the gauge by finding unplugging the harness connector on top of the fuel sender and locating the sender wire. With the key on, the gauge should read zero. If you provide a direct ground to the wire, the gauge should rise to the full mark. If that happens, then the gauge and circuit are good and the issue is with the sending unit. A leak at the fuel pressure hose will cause full fuel pressure, but has nothing to do with the sending unit. Voluntary recalls have a time limit, but, safety recalls mandated by the NHTSA will stay active until the recall is performed.
 

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Discussion Starter #7
I hate dead-end threads, so I'll continue to update this as I learn more. While not 100% conclusive, here's what I got.

ISSUE: Nissan code P1464 - Fuel Level Sensor Circuit. A quick Google search shows this as a known issue among Nissan Vehicles. It's a defect that Nissan never fixed. Based on my extensive research, 99% of the P1464 cases mentioned also include an erratic fuel gauge reading either below empty or above full. Clearly this indicates a bad Fuel Level Sensor Circuit or related wiring, so the code would be justified. What makes this situation unique is that my fuel gauge is working as designed, which means the sensor and its wiring are also working as designed. Yet despite being reset the code instantly comes back. I should note however that recently the code has been sporadic, clearing itself for a couple startups and then coming back.


EXPLANATION (unconfirmed): I spoke with a Nissan Service Tech who says "the issue is often caused by filling the tank while the engine is running." Apparently this confuses the system somehow. I always leave it running while refueling, so this made sense to me. However when I asked him about clearing the code by refueling with the engine off a few times he said it wouldn't work. The only way to permanently fix the code is (a) Replace the ECU or (b) replace the entire Fuel Level Sensor. He also stated the he couldn't guarantee that (b) would resolve it. At that point I became a bit heated. I asked the guy (in a 50% confused 50% pissed off tone) how this was not considered a factory defect and repaired for free by Nissan. He couldn't really couldn't give an answer for it. And honestly I didn't expect him to. It wasn't his fault. Besides, my anger was mostly because I thought the truck couldn't be inspected while throwing this code, but after he explained that San Antonio doesn't do emissions checks for inspections I felt relieved. Sure enough I was able to get it inspected with the code and MIL light on. Sadly this does not apply everywhere.




NOTE: This P1464 code is specific to your Nissan, so don't be confused by the generic OBDii P1464 - Air Condition Demand... code.
 

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Running your engine while refueling often caused evaporative emission system leak codes to get triggered, not fuel level sensor codes. He may have been a Nissan service tech, but that doesn't necessarily mean he knows what he's talking about! I was a Nissan Master Tech for 16 years and, unfortunately, there are a lot of guys like that!
The fuel level sensor harness should run along the top of the frame rail to the engine compartment where it merges into the engine compartment harness and eventually enters the passenger compartment through the firewall. If you are really determined to diagnose the problem, download a factory service manual for your Frontier and perform the step-by-step diagnostics for P1464. It should be in the Engine Control (EC) chapter. NissanHelp.com has downloadable chapters and Nico Club's site has full service manual downloads, both for free. The FSM will not only give you the diagnostic steps, but wiring diagrams, connector views, component check procedures, system description and everything you need to know to properly diagnose the problem.
 

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Josh - I have a 2004 Frontier (though 4-cylinder) and I get a P0462 engine code for MY fuel level sender - and like yours: my fuel gauge has never "not worked fine".

smj999smj tells me that about $100 for a new fuel level sender would "most likely" take care of that, and the pump would not need replacing. Of course, the entire assembly is also available. And the bed must be lifted or tank dropped for access.

Why the design is for that to trigger an engine code, don't know. But it does not look like we're the only ones afflicted with this plague.
 
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