System to lean (bank 1) - 1996 Ford Contour

P0171 ; Fuel Trim System Lean (Bank 1)
P0174; Fuel Trim too Lean (Bank 2)
fuel trim is system to modify injector pulse if system go lean it will go rich when the system is too much lean and is max.rich it code
look for 02 sensor bank 1 and 2 data
hope it helps

I've come across these codes before. In almost every case there was an air leak in the intake air hose (hose between the engine air filter & the throttle body). Inspect this hose & tubes attached to it. This is especially true when the lean code includes the comment 'at idle'
P2187 - System too lean at idle Bank 1
P0174 - System too lean Bank 2
P2189 - System too lean at idle Bank 2
P2195 = HO2S Signal Biased/Stuck Lean (Bank 1 Sensor 1)
P2270 = HO2S Signal Stuck Lean (Bank 1 Sensor 2)
P2272 = HO2S Signal Stuck Lean (Bank 2 Sensor 2)

P2187 & P2189 = In order to provide the best possible combination of drivability, fuel economy and emission control, the PCM uses a closed loop air/fuel metering system. The PCM monitors the HO2S signal voltage and adjusts fuel delivery based in closed loop fuel control. Changes in fuel delivery will be indicated by the long-term and the short-term fuel trim values. The ideal fuel trim value is around 0%. The PCM will add fuel when the HO2S signal is indicating a lean condition. Additional fuel is indicated by fuel trim values that are above 0%. The PCM will reduce fuel when the HO2S signal is indicating a rich condition. Reduction in fuel is indicated by fuel trim values that are below 0%. The DTC relevant to fuel trim will be set when the amount reaches excessive levels because of a lean or rich condition

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.

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.


I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

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

p0171-- system to lean (bank 1)----p0174-- system to lean (bank 2 ). bank 1 is the side that #1 cylinder is on. bank 2 is the other side. the cause may be bad 02 sensors on both banks, or a exhaust leak. also you may want to check and clean the mass air flow sensor. for the sensor will set the same code as 02 sensors. good-luck!!

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