Mechanics

CODE P171 & P172

2002 Mercury Mountaineer

Computer problem
2002 Mercury Mountaineer V8 Two Wheel Drive Automatic

my suv is beging to cut of at sto lights, what does code p171 & p172 mean?
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DORIS G HICKS
November 21, 2009.




P0171 & P0172 means that an oxygen sensor
in bank 1 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.

Causes: A code P0171 & P0172 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 can 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.
* There could be a fuel pressure or delivery problem.

I WOULD CLEAN THE MAF SENSOR WITH " SPRAY" ELECTRONICS OR BRAKE CLEANER. MAKE SURE IT IS " COMPLETELY" DRY BEFORE YOU REINSTALL IT.
CLEANING THE MAF USUALLY SOLVES THE PROBLEM 95% OF THE TIME.
The MAF sensor is located right near your air cleaner box. Right on the black rubber air flow tube, it is black and has " Air Flow" marked on it with an arrow pointing to the flow direction.

Possible other solutions include: * Inspect all vacuum and PCV hoses, replace if necessary

* Inspect fuel lines for cracks, leaks, or pinches
* Check the fuel pressure at the fuel rail
* Check the fuel injectors, they may be dirty. Use fuel injector cleaner or get them professionally cleaned/replaced.
* Check for an exhaust leak before the first oxygen sensor (this is unlikely to cause the problem, but it is possible).
I hope this information helped.
Good Luck; Rick

Tiny
RickMar
Nov 22, 2009.


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