SOURCE: What are the descriptions for
P0171 - System too Lean (Bank 1)
P0174 - System too Lean (Bank 2)
They have to do with fueling the engine. Usually when a car is running a less-than-optimal fuel mixture, it's traceable to O2 sensors, mass airflow sensor, or sometimes a coolant temperature sensor. These all have a direct effect on the fuel mixture. If your O2 sensors have been in the car for more than 60k miles, I'd change them first, as they have the biggest impact on fuel mixture. I don't know what year your car is, but if it's 95 or older, there is only one sensor per bank of cylinders. If it's 96 or newer, you'll have four - two before the catalytic converters, and two after them. The ones you'd want to change are the pre-cat O2 sensors, closest to the engine. These are used for determining fuel mixture. The post-cat O2 sensors are there for monitoring the cats' efficiency.
SOURCE: 2000 Prism 1.8 eng. code 8 [too lean code po171]
You could have a intake / exhaust leak or a problem with the the AIR system, MAF/VAF sensor, fuel pressure/pump, or injector(s), HO2s (oxygen sensors)
SOURCE: I have a 2000 chevy blazer 4.3l engine\is backfiring
Start by checking each cylinder for spark with a good spark tester. A misifre is either spark or fuel, so you can cut the problem in half. The engine light is probably on due to the misfire.
SOURCE: error codes PO171, PO174 on
P0171 means: System too lean (Bank 1) P0174 means: System too lean (Bank 2). Sounds like your injectors are not getting enough fuel.
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