P0172 CHEVROLET Fuel Trim System Rich Bank 1

Possible causes
– Faulty front heated oxygen sensor
– Ignition misfiring
– Faulty fuel injectors
– Exhaust gas leaks
– Incorrect fuel pressure
– Faulty Mass Air Flow (MAF) sensor
Tech notes
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
2000-2008 Chevrolet Factory Service Bulletin OBDII Code P0172

When is the code detected?
– Fuel injection system does not operate properly.
– The amount of mixture ratio compensation is too large. (The mixture ratio is too rich.)
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
– Excessive Fuel Consumption
P0172 CHEVROLET Description
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 Loop and Closed Loop. During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During Closed Loop, the ECM adds HO2S inputs to calculate the short and long term fuel trim (FT) adjustments. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. If the HO2S indicates a rich condition, the FT values will be below 0 percent. The short term FT values change rapidly in response to the HO2S voltage signals. The long term FT makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1.
CHEVROLET Technical Service Bulletins for P0172 code
2010 CHEVROLET EQUINOX ENGINE AND ENGINE COOLING:ENGINE
2010 CHEVROLET EQUINOX FUEL SYSTEM, GASOLINE:DELIVERY:FUEL PUMP
2007 CHEVROLET SILVERADO FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM:INJECTORS
2007 CHEVROLET SILVERADO 1500 FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM:INJECTORS
2007 CHEVROLET SILVERADO 2500 FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM:INJECTORS
2007 CHEVROLET SILVERADO 3500 FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM:INJECTORS
2007 CHEVROLET SUBURBAN 1500 FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM:INJECTORS
2007 CHEVROLET SUBURBAN 2500 FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM:INJECTORS
2007 CHEVROLET TAHOE FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM:INJECTORS
2008 CHEVROLET SILVERADO 1500 FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM:INJECTORS