What does code P0171 on a 2005 Ford Focus means?

Answer 1

It means that the PCM (the engine computer) has detected a "too lean" fuel-air mixture for the engine. In other words, the engine is not getting the correct (or THINKS it's not getting) the correct fuel-to-air mixture (not enough fuel, too much air). It is occurring on Bank 1. Could be as simple as a loose gas cap or could be one of several sensors that are malfunctioning -OR- you actually could have a problem with your fuel injectors, low fuel pressure from a malfunctioning fuel pump, clogged or dirty fuel filter, bad or leaking vacuum hose, bad Mass Air Flow Sensor or a manifold leak. Also could be as simple as a loose oil dipstick seating cap. If the Check Engine Light (CEL) is on constantly (not blinking) it's ok to drive it, but, get the actual problem diagnosed soon. If the CEL is blinking or there is any indication that the engine is hesitating or running rough, get it looked at by an ASE Certified Mechanic or the Dealership ASAP! If it's a simple thing like a loose fuel cap, it may take several engine cycles and at least 10-30 miles of driving to reset the light. DO NOT reset the light yourself by disconnecting the negative battery cable for 20-30 minutes as is advised in other i-net forums. You'll lose the "snap-shot" the computer took at the moment of the fault and may cause the problem to go un-repaired or difficult to diagnose. Average cost of fixing the P0171 problem is about $150 to $200 by a licensed, skilled mechanic. BTW - I did not mention the other five or six things that could be the problem . . I tried cleaning the Mass Air Flow sensor, tightening caps, looking for vacuum leaks on my 2005 Ford Focus ZX3 s, 2.0L Duratec. Ended up at a repair station. It was a bad sensor and it only cost me $149 to replace it.