How To Test The MAF Sensor: Diagnosing DTCs P0101, P0102, P0103 (2003-2007 2.4L Honda Accord)

In this tutorial, I'll show you an easy way to test the MAF sensor on your 2.4L Honda Accord and troubleshoot diagnostic trouble codes (DTCs):

• P0101: MAF Sensor Range/Performance Problem.
• P0102: MAF Sensor Circuit Low Voltage.
• P0103: MAF Sensor Circuit High Voltage

The MAF sensor test I'm gonna show you is done with a multimeter, no scan tool required. With your test results, you'll find out if the MAF sensor is working or if its bad.

APPLIES TO: This tutorial applies to the following vehicles:

• 2.4L Honda Accord: 2003, 2004, 2005, 2006, 2007.

Symptoms Of A Bad MAF Sensor

As you're probably already aware, the mass air flow (MAF) sensor measures the amount of air entering the engine. The fuel injection computer then uses this info to determine the correct amount of fuel to inject into the engine.

If the MAF sensor malfunctions or fails, the fuel injection computer will no longer correctly adjust the air/fuel mixture and engine performance is gonna suffer. You'll see one or more of the following problems:

• Check Engine Light: The check engine light will be shining nice and bright on your dashboard and one of the following diagnostic trouble codes will stored in the computer's memory:
  • P0101: MAF Sensor Range/Performance Problem.
  • P0102: MAF Sensor Circuit Low Voltage.
  • P0103: MAF Sensor Circuit High Voltage
• Poor Engine Performance: You may experience a lack of power or hesitation during acceleration, especially under heavy loads or at higher speeds.
• Rough Idling or Stalling: The engine may idle rough or even stall unexpectedly.
• Decreased Fuel Efficiency: A faulty MAF sensor can disrupt the air-fuel mixture, causing the engine to run either too rich (excessive fuel) or too lean (insufficient fuel). The end result is bad gas mileage.
• Black Smoke from Exhaust: An overly rich air-fuel mixture due to a faulty MAF sensor can result in black smoke coming out of the exhaust pipe.
• Difficulty Starting: In some cases, a failing MAF sensor may cause difficulty starting the engine.
• Stalling at Idle: The engine may stall when idling.
• Hesitation or Surging: You might notice hesitation or surging during acceleration or while driving at a consistent speed.

MAF Sensor Circuit Descriptions

In order to correctly diagnose the MAF sensor as good or bad, we need to know what each of the five wires coming out of the connector is doing.

The following table provides a brief description of each wire:

Terminal	Wire	Description
1	Black with yellow stripe (BLK/YEL)	12 Volts
2	Black with red stripe (BLK/RED)	MAF Sensor Ground (provided by PCM)
3	Red with green stripe (RED/GRN)	MAF Sensor Signal
4	Red with yellow stripe (RED/YEL)	IAT Sensor Signal
5	Green with yellow stripe (GRN/YEL)	IAT Sensor Ground

Where To Buy The MAF Sensor And Save

The following MAF sensors are of known automotive brands (brands that I use myself):

NOTE: Not sure if the indicated MAF sensors fit your particular Ford Fiesta? Don't worry. Once you get to the site, they'll ask you for the specifics of your particular vehicle. If it doesn't fit, they'll find you the right one.

TEST 1: Testing The MAF Signal Key On Engine Off

To get started, we're gonna check the MAF sensor's output signal and make sure that it's 0.5 Volts with the key on but with the engine off.

The wire that we'll tap into, to check this voltage, is the red with green stripe (RED/GRN) wire of the MAF sensor's 5-wire connector.

In the photo above, I've labeled the RED/GRN wire the the number 3.

IMPORTANT: The MAF sensor must be connected to its connector to perform this test. You'll need to use a back-probe on the connector or a wire-piercing probe on the wire. You can see an example of this tool here: Wire Piercing Probe Review (Power Probe PWPPPPP01).

Let's get started:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Connect the black multimeter test lead to the battery (-) negative terminal.

3. 3

   Connect the red multimeter test lead to the wire labeled with the number 3 using a suitable tool.
   
   This is the red with green stripe (RED/GRN) wire of the 5-wire connector.

4. 4

   Turn the key to the ON (II) position but don't crank or start the engine.

5. 5

   The multimeter should register 0.5 Volts.

Let's see what your test results mean:

CASE 1: The multimeter registered 0.5 Volts. This is the correct test result. Your next step is to check the MAF signal with the engine running.

For this test go to: TEST 2: Testing The MAF Signal Key On Engine Running.

CASE 2: The multimeter registered 0.1 Volts or less. This test result confirms trouble code P0102: MAF Sensor Circuit Low Voltage.

This usually means one of two things, the MAF sensor isn't getting power or the MAF sensor is bad.

In this particular case, your next steps are to:

1. Check if the sensor is getting 12 Volts (TEST 3).
2. Check the MAF signal with the engine running (TEST 2).

If your test results indicate that the MAF sensor is getting 12 Volts (TEST 3) and that it's NOT creating a voltage signal that increases/decreases as engine speed increases/decreases (TEST 2), the MAF sensor itself is bad.

For the first of these two tests, go to: TEST 3: Making Sure The MAF Sensor Is Getting Power.

CASE 3: The multimeter registered 5 Volts or more. This test result confirms trouble code P0103: MAF Sensor Circuit High Voltage.

This usually means one of two things, the MAF sensor isn't getting Ground or the MAF sensor is bad.

In this particular case, your next steps are to:

1. Check if the sensor is getting Ground (TEST 4).
2. Check the MAF signal with the engine running (TEST 2).

If your test results indicate that the MAF sensor is getting Ground (TEST 4) and that it's not creating a voltage signal that increases/decreases as engine speed increases/decreases (TEST 2), the MAF sensor itself is bad.

For the first of these two tests, go to: TEST 4: Making Sure The MAF Sensor Is Getting Ground.