DTC P0174 – How To Service a Ford Taurus MAF

DTC P0174 – How To Service a Ford Taurus MAF


This OBD-II trouble code P0174 is a Diagnostic trouble code that shows your Ford Taurus is running a tad lean in Bank 2. Because your Ford PCM receives several different engine signals to properly operate the vehicle, there can be many causes to this DTC check engine light.

Specific verbiage of this diagnostic trouble code is System Too Lean (BANK 2), and it means that the oxygen sensor on that side of the motor (BANK 2, typically the side opposite cylinder 1) is running lean, or without sufficient fuel.

Today we’ll be showing you how to resolve the OBDII DTC P0174 in a 2004 Ford Taurus with the 3.0 liter flex fuel engine in it. If your Ford has a P0174 trouble code, chances are you also have a P0171 trouble code as well. While there’s a few possible problems that can cause this trouble code as shown below, we’ll be showing you how to service a Ford Taurus MAF to fix our P0174 trouble code.


Symptoms of DTC P0174


  • Lack of power
  • Bad fuel economy
  • Detonation
  • Trouble starting
  • Engine Failure
  • Piston Ring failure

Possible Causes of P0174


  • Leaking air tract
  • Leaking Mass Air Flow Sensor
  • Bad Mass Air Flow Sensor
  • Bad Injector
  • Bad Fuel Pump
  • Bad oxygen sensor

Because we’ll be walking you through how to service a Ford Taurus MAF sensor, we’ll be assuming you have already checked your intake snorkel and tract for any leaks.


How to Check your Ford Taurus for intake leaks – Use a small bottle of soapy water and gently spray over your intake snorkel and intake. Never spray into the engine or into an open air element filter. Look for bubbling or hissing noises, which will show you where the leak in the intake tract is.


This is typically the biggest reason for this lean condition and this OBDII trouble code P0174 to trigger. One of the most common questions posed to us is “Where is my Mass Air Flow (MAF) Sensor?”.

To locate your MAF sensor, take a look at the driver side of the engine bay to locate your air box. The Mass Air Flow Sensor is mounted to the airbox by way of 4 10mm bolts.

If you are replacing your MAF Sensor, you do not need to remove the air box, but you will need to undo the mass air flow sensor by removing the two hex bolts.



The replacement Ford part number for this mass air flow sensor is 3W4Z-12-B579-AB and when you are replacing your Ford Taurus MAF, make sure to insert the new MAF according to the air flow arrow.

If you are uncertain if your MAF is the problem, and need to know how to test your Ford Taurus MAF, you’ll need a voltmeter or multimeter to conduct a test.


We’ll be testing the Mass Air Flow Sensor for power and ground to see if it’s being powered on during the KEY ON position. Insert your ignition key and turn the ignition switch to the “ON” position but without starting the engine.

Locate and find your MAF to begin the How To Service a Ford Taurus MAF steps and check your MAF for functionality. Unplug the MAF sensor and take a look at the back of your wiring harness, you will be using your voltmeter or multimeter to check the wiring of the MAF plug.


Connect the black lead of your multimeter to the negative terminal of your battery and backprobe PIN 2 shown above. This is a red wire and it’s the second wire from the left if you are facing the engine harness from the back.

There should be a voltage signal here with the key set to the “ON” position. If you do not get 12 volts here, this is a good reason why your P0174 or P0171 trouble code is lit on your dashboard.

The next wire is the white wire with black stripe through it, and this wire is PIN 1 which should be the low reference ground signal. This signal is sent from the ECU and PCM, and should never be teed with a multimeter when testing for power.

Always remember to backprobe your MAF connector, never insert the lead of your multimeter from the front of the plug. Doing so may result in damage to your plastic connectors and compromise your vehicle’s operation.


Because this Ford mass air flow sensor is a 5 pin unit, this means that the air intake temperature sensor is also incorporated into the Ford Taurus MAF sensor. To check power to your AIT sensor located inside your Ford Taurus MAF, check the PIN 3 which is the last pin on the right hand side of your MAF connector.

There should be 5 volts here delivering power to your Intake temperature sensor. If you have voltage here, there’s nothing wrong with the power and ground wiring to your MAF sensor, and you should go ahead and replace it. Once you have your Ford Taurus MAF replaced, connect a datalogger or scan tool to erase the P0174 trouble code.

That does it for our How To Service a Ford Taurus MAF, for more technical How-To’s and articles subscribe to My Pro Street.