Im getting P0171 code- lean .

Did you view sensor data parameters on a professional type scan tool ? What are the fuel trim's at ? long term & short term , Are the O2 sensors switching normally , MAP sensor data etc.... What kind of vehicle are we talking about ? The fuel pressure droping a couple PSI doesn't mean the fuel pump is bad . Suggest you take it to a qualified repair shop.

• DTC P0171 Fuel Trim System Lean Bank 1
• DTC P0174 Fuel Trim System Lean Bank 2
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The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the ECM determines fuel delivery based on sensor signals without oxygen sensor (O2S) input. During Closed Loop, the O2S inputs are added and used by the ECM to calculate short and long term fuel trim (FT) fuel delivery adjustments. If the O2S indicates a lean condition, FT values will be above 0 percent. If the O2S indicate a rich condition, FT values will be below 0 percent. Short term FT values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term FT makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the ECM detects an excessively lean condition, DTC P0171 or P0174 sets.
Diagnostic Aids
• Excessive resistance in the fuel injector ignition 1 voltage circuit or the fuel injector control circuit may cause the following symptoms:
- Lean condition
- Misfire
- Rough idle
• The system will go lean if an injector is not suppling enough fuel.
• A lean condition could be present during high fuel demand.
• A malfunctioning MAF sensor can cause this DTC to set. Refer to DTC P0101 .
• Review the Failure Records with a scan. If an intermittent condition is suspected, refer to Intermittent Conditions .

DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0420 Catalyst System Low Efficiency Bank 1
• DTC P0430 Catalyst System Low Efficiency Bank 2

This code could mean the catalytic converter on that bank has failed .

Causes of lean condition trouble codes P0171 P0174 GM 5 3L

P0420 P0430 catalytic converter catalyst inefficiency code diagnosis

• Dale, code P0171 fuel system too lean
• Possible causes
• change fuel filter first, if it has not been done recently

RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SENSOR
O2 SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
O2 SENSOR HEATER OPERATION
TPS VOLTAGE GREATER THAN 0.92 VOLTS WITH THROTTLE CLOSED
TP SENSOR SWEEP
MAP SENSOR OPERATION
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR (HIGH)
PCM
Check the attached links,
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2000 Jeep Grand Cherokee p0171

Possible problems related to Code P0171 Jeep Garage Jeep Forum

P0171 System to Lean Bank 1

Code P0171

If Short term # is high while underway, but normal while idling, you could have a scewed maf signal. Sometimes cleaning maf with carb cleaner helps. If no intake leaks are found, and fuel pressure and volume are ok, it could be maf sensor.

First of all, what kind of car is this? Second, this is a lean code. Now, if you really have no intake leaks or restricted fuel issues, one possibility is scewed maf signal during higher rpms. If you can, monitor your Short Term fuel trim at normal highway speeds.If it is high, then and lower at idle, you may need a maf sensor.
Hope this helps

Hi there:
The Powertrain Control Module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During Closed Loop the PCM adds oxygen sensor inputs to calculate Short and Long Term fuel trim (fuel delivery adjustments). If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent . If the oxygen sensors (O2S) indicate a rich condition, fuel trim values will be below 0 percent. Short Term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long Term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, this diagnostic trouble code (DTC) will set.



Check HERE additional details to test and check.


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Check engine light on ? Lean codes , fuel trims ? Causes of lean condition trouble codes P0171 P0174 GM 5 3L

Do you know what a professional type scan tool is ? What fuel trims are . How to find a lean condition ? Understanding Short Term and Long Term Fuel Trim an SD Premium video

Trouble code P0171 means: Fuel System Lean (Bank 1)

The "lean condition" code is set when the long-term fuel trim value reaches a certain setpoint, +14% if I remember right. Whatever is going on, the PCM thinks the car is running lean. It could be a faulty O2 sensor (or the wiring), a fault in one of the other sensors that are used for the fuel trim calculations (IAT, MAP, TPS, coolant temp, battery temp, rpm, or any of the wiring associated with those), or an actual lean condition caused by a problem with one of the fuel delivery devices (fuel pump, fuel filter, fuel pressure regulator, fuel injector, or any of the wiring or tubing associated).

P0171 indicates a lean condition. The most common cause of this is a defective mass air flow sensor. Also check if any vacuum leaks.Replace MAf sensor,if cleaning the MAF does not help.
OBD II P0172 Fuel System Too Rich (Bank 1).P0172 - System Too Rich (Bank 1) Essentially this DTC means that an oxygen sensor in bank 1 detected a rich condition.
When the code says that the Fuel System is "too rich," it means that the computer has been subtracting more and more fuel, which is called Long Term Fuel Trim. Ideally, the Long Term Fuel Trim should be close to 1 to 2 percent. When a code P0172 is set, it means that the Fuel Trim is anywhere from -15 percent to as low as -30 percent compensated. When this happens, the computer knows that there is an improper condition in the control of the Fuel System.


Thanks.

Trouble Code: P0171 (3.8L V6 VIN 1 Auto)
Fuel Trim System Lean (Bank 1) Print this code data Number of Trips to Set Code: 2
OBD II Monitor Type: CCM Details
Indicators: MIL Details

• Fuel Details
• MIL Details

Trouble Code Conditions:
DTC P0101-P0103, P0107, P0108, P0121-P0123, P0130-P0138, P0140, P0141, P0201-P0206, P0300, P0401-P0405, P0410, P0440-P0446, P0506, P0507, P1404 or P1441 not set, engine started, vehicle driven at less than 82 mph at 550-4000 rpm, BARO sensor over 70 kPa (10.1 psi), ECT sensor from 68-230ºF, IAT sensor from 64-158ºF, MAF sensor from 2.8-150 gm/s, MAP sensor from 16-105 kPa (2.6-15.2 psi), fuel level over 10%, and the PCM detected the Long Term fuel trim value was more than +20% for 6 seconds. The PCM controls the air/fuel metering system to good overall fuel economy, driveability, and emission control. During open loop, the PCM determines fuel delivery based on sensor signals, without the oxygen sensor input. During closed loop, the PCM adds oxygen sensor inputs to calculate Short and Long term fuel trim fuel delivery adjustments. Short Term fuel trim values change rapidly in response to changes in the oxygen sensor signals. Long Term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1.

Possible Causes:

• Air leaks in intake manifold, exhaust pipes or exhaust manifold
  
• Fuel control sensor is out of calibration (ECT, IAT or MAF)
  
• Low fuel pressure (fuel filter clogged, pressure regulator failure)
  
• One or more injectors restricted or pressure regulator has failed
  
• HO2S element is contaminated, deteriorated or has failed
  
• Vacuum hose is disconnected, broken, leaking or loose
  

Troubleshooting:2002 Buick Park Avenue, 3.8L, P0171