What is code p0171 on a Ford Focus 2.0l Z tech?

Answer 1

Code P0171 System too lean bank one

The focus had a problem with the PCV Tube collapsing. Over time this makes a hole in the tube causing a large vacuum leak.

Symptoms

You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

Causes

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

• The MAF (Mass Air Flow) Sensor is dirty or faulty. 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.

• There could be a vacuum leak downstream of the MAF sensor.

Possible solutions include:

• In the vast majority of cases, simply cleaning the MAF sensor does the trick. 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 if necessary
• Check for a dirty fuel filter and proper fuel pressure

On my 1998 Ford F150 i replaced the fuel filter, air filter and i cleaned the MAF (Mass

Air Flow Sensor) with a can of Mass Air Flow Sensor Cleaner. I then disconnected the NEG battery cable for about 30 minutes to reset the error code. That fixed the problem for me.

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I have a 1998 F150 5.4 - the failure on mine was a vacuum leak at the throttle body end of the pcv line.