A Ford P0171 is a LEAN code for cylinder financial institution 1, and P0174 is actually a LEAN code for cylinder financial institution 2. These codes usually come about on quite a few Ford vehicles, and therefore are set when the powertrain management module (PCM) sees the air/fuel mixture is running too lean (also significantly air, not ample fuel).

If the Check Engine Light comes on, either one of these codes, or each, may be uncovered whenever a code reader or scan tool is plugged to the car diagnostic connector. When the car is driven long sufficient, commonly both codes will be set.

A P0171 lean code for bank 1 is definitely the cylinder financial institution about the Suitable (passenger) side on the engine on Ford automobiles using a V6 or V8 engine and rear-wheel drive.

A P0174 lean code for bank 2 would be the cylinder financial institution on the LEFT (driver) side of the engine on Ford autos by using a transverse-mounted V6 engine and front-wheel drive. This code will not be set on 4 cylinder engines (no financial institution 2).

A lean fuel condition may exist in the event the engine is sucking in too considerably air and/or the fuel system is not providing adequate fuel. If undesirable sufficient, a lean fuel affliction may possibly result in lean misfire, a rough idle, hesitation or stumble when accelerating, and/or poor engine effectiveness.

Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor that may be not studying airflow accurately, an EGR valve is just not closing and is leaking exhaust to the intake manifold, an EGR valve that’s making it possible for also much flow (since the EGR differential pressure sensor that monitors EGR flow is faulty and it is under-reporting EGR flow).

Should the dilemma is just not adequate fuel, the underling lead to might be a weak fuel pump, restricted fuel filter, leaky fuel strain regulator or dirty fuel injectors.
Ford MAF sensor


One with the most typical causes of Ford P0171 and P0174 lean codes is actually a dirty mass airflow (MAF) sensor. The MAF sensor is located within the air inlet tube
just ahead with the throttle body. The MAF sensor should be shielded from outside dust and debris by the air filter, but at times the air filter doesn’t match genuine tight inside the housing and allows unfiltered air to the engine. Dirt can stick to the MAF sensor wire and kind a coating that slows the response from the sensor to improvements in airflow. The MAF sensor can be contaminated by fuel vapors that back up with the consumption manifold and throttle body if the engine is shut off. The vapors can leave a waxy coating within the sensor wire. This causes the MAF sensor to underneath report airflow, which in turn misleads the powertrain management module (PCM) so it doesn’t add ample fuel to maintain a effectively balanced air/fuel ratio. Because of this, the engine runs lean and sets a P0171 and/or P0174 code (see Ford TSB 98-23-10 for particulars).

If the MAF is dirty, the repair is easy adequate: just clean or substitute the MAF sensor. In many circumstances, the MAF sensor could be efficiently cleaned by spraying the sensor component with electronics cleaner. Don’t use any other kind of cleaner as this could harm the sensor.

Disconnect the air inlet tube just ahead on the sensor, and then spray the electronics cleaner through the display with the wire component within the center in the little MAF sensor. Let the cleaner soak in for many minutes, then give it another shot of cleaner. Let it sit an additional five minutes, then reconnect the air inlet tubing and start the engine.

In case the lean codes keep coming back, the MAF sensor may have to become replaced should the engine does not have a vacuum leak or fuel delivery trouble.
Ford fuel pressure regulator


Yet another prevalent cause of Ford P0171 and P0174 ean codes is definitely an engine vacuum leak. Ford TSB 04-17-4 details procedures for checking fuel trim and searching for vacuum leaks.

On 3.8L Fords using a split-plenum consumption manifold, the port gaskets and isolator bolt assemblies for your upper plenum can deteriorate above time and leak air, frequently as a result of oil currently being sucked in to the consumption manifold throughout the PCV system. Also the vacuum hose that connects the fuel pressure regulator for the intake manifold can swell and leak vacuum the place the hose connects to your manifold. Ford TSB 03-16-1 says the repair will involve many methods: remove the upper manifold plenum and replace the authentic gaskets and bolts with revised ones, replace the front valve cover using a revised valve cover that decreases the amount of oil vapor sucked into the PCV system, inspect and substitute the fuel stress regulator hose, and finally, reflash the PCM so it is actually significantly less sensitive to lean fuel disorders.

Ford DPFE sensor


Ford p0171 AND p0174 lean codes can be set by a undesirable EGR differential stress sensor. These sensors have a pretty large failure price when a vehicle has much more than about 60,000 miles about the odometer or is more than five or six many years outdated.

The DPFE sensor is mounted about the engine, and is connected with two rubber hoses to your tube that routes exhaust gasoline towards the EGR valve. The unique equipment sensor has an rectangular aluminum housing about three inches lengthy. Corrosion in the sensor lowers its sensitivity to EGR flow, triggering it to under-report EGR flow. The PCM responds by expanding EGR flow, which may retain the EGR valve open longer than usual making a lean condition in the engine. Thus, a negative sensor may possibly set a P0401 code (insufficient EGR flow), or it may not set an EGR code but a P0171 and/or P0174 lean code as a substitute.

The lead to in the P0401 code in many scenarios turns out to be a bad DPFE sensor, not an EGR valve dilemma or an EGR valve that is definitely plugged up with carbon (although this could also set a P0401 code). An aftermarket replacement DPFE sensor charges much less than $50 and usually gets rid of not merely the P0401 code, but in addition the P0171 and P0174 codes, too.