The Clean Air Act of 1990 requires that any car or light truck newer than 1995, including Dodge Ram, have an on-board diagnostic (OBD) computer to monitor emissions control and other vehicle systems. The OBD captures a standardized code when a system is suspected of malfunction.
The automotive industry calls the second-generation OBD computers OBD-II. An OBD-II computer stores a malfunction code in its memory, which can be read with a hand-held scanning device.
An OBD-II monitors an array of electronic sensors throughout the engine and other vehicle systems. When a sensor reads outside its specified range, the computer turns on the "Check Engine" light and stores a five-character standardized code in memory. The code indicates which sensor has triggered the trouble alert.
The standard set of codes is widely published in owner's manuals and on websites dedicated to auto repair. Many sites also suggest possible causes for the malfunction and their remedies.
P0171 is the code for a fuel injection system problem. A sensor has reported that the air-fuel mixture is too lean, meaning that there is too much oxygen in the exhaust. If the sensor is correct, you may experience some knocking, hesitation on acceleration or a lack of power.
A code P0171 often is caused by a dirty Mass Air Flow (MAF) sensor, or a vacuum leak in the air circuit between the MAF sensor and the engine. Low fuel pressure caused by a faulty fuel pump or dirty fuel filter also may cause a P0171 error.
