P0171 CHEVROLET – Fuel Trim System Lean Bank 1

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What does that P0171 mean?

Basically, this means that an oxygen sensor in bank 1 has detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1. The P0171 is one of the more common trouble codes.

This code is triggered by the first downstream (front) O2 sensor. The sensor provides a reading of the air: fuel ratio leaving the engine’s cylinders, and the vehicle’s powertrain/engine control module (PCM/ECM) uses that reading and adjusts to keep the engine running at that optimum ratio of 14.7:1. If something is not right and the PCM cannot maintain the 14.7:1 ratio, but rather there is too much air, it triggers this code.

The P0171 code could also be caused may be caused by one or more of the following: debris on MAF sensor causing an incorrect reading, improper oil level, low or high fuel pressure or Engine Control Temperature (ECT) Sensor reading inaccurate.

There is a factory service bulletin for the following Chevrolet models:

2000 Chevrolet S-10

2000-2008 Chevrolet Camaro

2000-2008 Chevrolet Lumina

2000-2008 Chevrolet Cavalier

2000-2003 Chevrolet Impala

2000-2003 Chevrolet Malibu

2000-2003 Chevrolet Monte Carlo

2000-2003 Chevrolet Silverado

2000-2003 Chevrolet Suburban

2000-2003 Chevrolet Tahoe

2000-2003 Chevrolet Venture

2001-2008 Chevrolet Express

2002-2008 Chevrolet Astro

2000-2003 Chevrolet Avalanche

2000-2003 Chevrolet Trailblazer

2003-2008 Chevrolet Blazer

2003-2008 Chevrolet S-10

2003-2008 Chevrolet Trailblazer EXT

When is the P0171 code Detected?

Fuel injection system does not operate properly.

The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)

P0171 Chevrolet Possible Symptoms

There may be symptoms such as:

Engine Light ON (or Service Engine Soon Warning Light)
Excessive Fuel Consumption
Performance problems, such as a lack of power on acceleration and some “coughing” or misfiring
Detonation (spark knock)
Rough idle
hesitation/surge on acceleration.
The vehicle may have trouble idling, especially when warm or when sitting at a stoplight

P0171 Chevrolet Possible CAUSES

P0171 Chevrolet may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty
There could be a vacuum leak downstream of the MAF sensor
Faulty or stuck open PCV valve
Failed or faulty oxygen sensor (bank 1, sensor 1)
Sticking/plugged or failed fuel injector
Low fuel pressure (possible plugged/dirty fuel filter!)
Exhaust leak between engine and first oxygen sensor
Intake air leaks
Faulty front heated oxygen sensor
Ignition misfiring
Incorrect fuel pressure
Lack of fuel
Incorrect Positive Crankcase Ventilation (PCV) hose connection

Note: The use of “oiled” air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.

P0171 Chevrolet Possible Solutions

Cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. So, possible solutions include:

Clean the MAF sensor. Consult your service manual for it’s location if you need help. I find it’s best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it’s dry before reinstalling
Inspect all vacuum and PCV hoses, replace/repair as required
Inspect all hoses and connections in the air intake system
Inspect and/or test the intake manifold gaskets for leakage
Check for a dirty fuel filter and proper fuel pressure
Ideally you’ll want to monitor short and long term fuel trims using an advanced scan tool
If you have access, you may want to run a smoke test

Also, Read P0340 NISSAN Fault Code Problem Solution

Misdiagnosis for the P0171 code

Oxygen sensors

Additional Causes of Code P0171

A plugged Fuel Filter or poorly functioning Fuel Pump can set the P0171 code. The computer hears (accurately) from the Oxygen Sensor that the Fuel Mixture is too lean so the computer keeps increasing the amount of fuel being delivered into the combustion chambers. But in this case, the Fuel System can’t increase the amount of fuel.
If you still can’t find the problem, be sure to check and verify that fuel pressure and delivery are at spec. If fuel pressure and volume check out okay, scope the injectors and perform injector drop and/or flow tests to see if they are capable of delivering enough fuel. Dirty/contaminated gas can definitely plug injectors and trigger these lean codes.

P0171 CHEVROLET – Fuel Trim System Lean Bank 1