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Hello!
so I keep getting the p0171 and 174 codes on a 2013 gx 460. The MAF and fuel pump have both been changed, while doing live performance stats both banks 1 and 2 are reading a 20% on short term fuel trim, and 44% on LTFT under load. Now while at idle STFL is 3% (1) and 5% (2). LTFT isthe same at 44%. Upon starting it maybe be right away or will go through a entire starting cycle plus half of a second cycle.
no one in my area will touch the vehicle until next week and if its something bad it has to get towed to the nearest dealer which is 250 miles away. So any guidance on this would be greatly appreciated
I just went through the same nightmare on one of our non-Lexus SUVs. Unfortunately there are a ton of things that can cause this so I would:
1. Do a smoke test. There are some YT videos that show you how you can make your own smoke test "device" (I made mine out of an empty paint can and old soldering iron) unless you want to wait for an order.
2. It appears that the GX has a separate pressure regulator (PN: 2328038061), that would be the next to rule out (see Fuel Pressure post, 46.5-47.4 PSI, if a bit higher that will not cause lean condition).
3. Pull, inspect clean fuel injectors, clogged fuel injector(s) will cause lean condition. There are ways you can clean the injectors, you need a kit to do that, but injectors are $50 a piece so it's worth it. Make sure you have replacement seals on hands if doing this.
4. Bad O2 sensors, if you are over a 100ks and on the original sensors I would just replace at least the upstream ones.
5. Move on to inspect, clean, replace the EGR, PCV valves.
I really hope #1 or #2 will solve your issues. In my case one of our "know it all" teenagers ran our of fuel and the truck never started again even after putting fuel into. Once I got it running P0171 and P0174 popped up immediately but my trim was slightly better than the numbers you posted. I ended up replacing both the fuel pump and filter with built in regulator. The fuel pressure was 5PSI below the minimum causing the lean condition.
If the nearest dealer is 250 miles away I would not drive the truck that long unless you know what the problem is. Lean condition may (or may not) damage the engine. There are all sorts of theories our there about how serious it is, some say it won't cause overheat, some say that the less fuel vapor does not cool the incoming air enough (in case of turbo chargers this may make a difference). But it is your tuck and your decision.
07-20-22, 03:57 PM
P0171 and P0174
