Lean bank 1 and 2 - 1998 Ford Expedition

It means that one side of the engine cylinders are running too lean of a fuel mixture Bank one is the left side of the engine. Put a fuel injector cleaner in the gas tank first. Once it has had time to do its work, test again. If it's still lean, then look at the injectors and the control module for a fix.

P0171 system too lean bank 1
P0174 system too lean bank 2
links to information on the codes

it means that the O2 sensors in your vehicle detected a lean condition in their respective banks. this could be caused by a dirty MAF (mass air flow) sensor or a vacuum leak downstream from the MAF sensor

sometimes you can clean the MAF with electronics cleaner or brake cleaner but be sure to take it off the vehicle first. be careful not to damage the MAF while spraying the cleaner, and allow it to dry completely before installing it on the vehicle.

Bank 1 = drivers side (IE: 02 sensor bank1 = driver O2 sensor pre cat. converter)

P2197 - Oxygen Sensor Signal Biased/Stuck Lean Bank 2 Sensor 1
P2187 - System Too Lean At Idle Bank 1
P2177 - System Too Lean Off Idle Bank 1
P2195 - Oxygen Sensor Signal Biased/Stuck Lean Bank 1 Sensor 1
P2179 - System Too Lean Off Idle Bank 2

I am not sure what your Mazda is, but from the sounds of it, both of your Oxygen Sensors are shot. Replace them both, or check for vacuum leaks. It may be a good time to inspect and replace the PCV Valve and PCV Valve hose, too.

code P1128 02 sensor bank 1 lean
code P1129 02 sensor bank 1 lean to limit
code P1133 02 sensor bank 2 lean
code P1134 02 sensor bank 2 lean to limit

fuel system is lean.

P0313 - Misfire Detected with Low Fuel
P0174 -System too Lean (Bank 2).
P0171 -System too Lean (Bank 1).

P0171 and P0174 mean "system too lean" for banks 1

Possible O2 sensors:

P2270 O2 Sensor Signal Stuck Lean Bank 1 Sensor 2
P2271 O2 Sensor Signal Stuck Rich Bank 1 Sensor 2
P2272 O2 Sensor Signal Stuck Lean Bank 2 Sensor 2
P2273 O2 Sensor Signal Stuck Rich Bank 2 Sensor 2
P2274 O2 Sensor Signal Stuck Lean Bank 1 Sensor 3
P2275 O2 Sensor Signal Stuck Rich Bank 1 Sensor 3
P2276 O2 Sensor Signal Stuck Lean Bank 2 Sensor 3
P2277 O2 Sensor Signal Stuck Rich Bank 2 Sensor 3
P2278 O2 Sensor Signals Swapped Bank 1 Sensor 3 / Bank 2 Sensor 3
---
This is Bank 1 (closer to the dash panel) Sensor 2 (located after the catalytic converter).

---
Note: A malfunctioning front oxygen sensor may cause fuel trim codes to set.

1. Several Diagnostic Trouble Codes use specific terminology to refer to sensor location. The illustration and key below explain the following terms:
2. Engine BANK Bank 1 is closer to the dash panel, (also referred to as RH or right hand). Bank 2 is closer to the radiator, (also referred to as LH or left hand).
3. UP Refers to Sensor 1 or "front sensor". It is located closer to the exhaust manifold and before the catalytic converter.
4. DOWN Refers to Sensor 2 or "rear sensor." It is located after the catalytic converter.
5. The following examples show how to interpret oxygen sensor terminology:
6. B1/S1 = Bank 1/Sensor 1 = Dash panel side, BEFORE the catalyst or "upstream"
7. B2/S2 = Bank 2/Sensor 2 = Radiator side, AFTER the catalyst or "downstream"

This can be caused by a faulty mass air flow sensor

P0171------ system too lean bank#1
Po174------ system too lean bank#2
For these 2 codes, try cleaning the maf sensor (mass air flow), that is mounted in the big black hose that goes from the air filter housing to the throttle plate, if it is dirty, that will cause those 02 sensors to send a signal to the computor to lean the air fuel mixture. If cleaning it doesn't work, the sensors will probably need changing.
P0300---- Random/multiple cylinder misfire
P0316---- Cylinder misfire at start up---- first 100 revolutions.
On those 2 codes, you have to do some testing to find out why there is a misfire.
Possible causes:
dirty/malfunctioning injectors
weak coil pack
fowling spark plugs/wires
Low fuel pressure