How To Test The MAF Sensor (1997-2002 2.0L SOHC Ford Escort, Mercury Tracer)

The mass airflow (MAF) sensor on the 1997-2002 2.0L SOHC Ford Escort (Mercury Tracer) can easily be tested with a multimeter (you don't need a scan tool).

In this tutorial, I'm going to walk you through the whole process of testing it with a multimeter. These are four tests that include checking its output voltage MAF signal, making sure it's getting power (VPWR), and Ground (both PWR GND and MAF RTN).

Although the MAF sensor on your Ford Escort (Mercury Tracer) is inside the round air filter canister assembly and hidden from view, it can be easily diagnosed as good or bad in four easy tests.

You can find this tutorial in Spanish here: Cómo Probar El Sensor MAF De 2.0L Ford Escort, Mercury Tracer (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following 2.0L Single Overhead Cam (SOHC) 2.0L equipped vehicles:

• 2.0L SOHC Ford Escort: 1997, 1998, 1999, 2000, 2001, 2002.
• 2.0L SOHC Mercury Tracer: 1997, 1998, 1999.

ZX2 MAF SENSOR TESTS: The Ford Escort ZX2 uses a six wire MAF sensor. You can its MAF sensor tests here:

• How To Test The MAF Sensor (1998-2003 2.0L DOHC Ford Escort ZX2).

Common Symptoms Of A Bad Ford MAF Sensor

The check engine light will definitely be lit on your instrument cluster and your Escort (or Tracer) may also display one or several of the following symptoms:

1. MAF trouble codes that light up the check engine light (CEL) on your instrument cluster.
   • P0102: MAF Signal Low Input to PCM.
   • P0103: MAF Signal High Input to PCM.
2. MAF sensor malfunction that DOES NOT light up the check engine light (CEL).
3. Lean and/or Rich code(s).
4. Fuel trim code(s).
5. A tremendous lack of power upon acceleration.
6. Black smoke coming from the tail-pipe.
7. Bad gas mileage.
8. Vehicle may idle rough and stall.

Circuit Descriptions Of The Ford MAF Sensor's Connector

Your Ford Escort or Mercury Tracer's MAF sensor has four wires coming out of its connector. In the table below, you'll find a brief description of what each wire (circuit) does to help us in the tests that follow.

Pin	Wire	Description
2	Red (RED)	VPWR –12 Volts Input in RUN or START
3	Black with white stripe (BLK/WHT)	PWR GND –Chassis Ground Input
4	Tan with light blue stripe (TAN/LT BLU)	MAF RTN –MAF sensor Ground (provided by PCM)
5	Light blue with red stripe (LT BLU/RED)	MAF –MAF signal

IMPORTANT: All of the tests are ON CAR TESTS, do not remove the mass air flow sensor from the vehicle or from its plumbing.

TEST 1: Testing The MAF Signal

The very first thing we're going to check (to see if the MAF sensor is good or bad) is to tap into the light blue with red stripe (LT BLU/RED) wire —the MAF signal output wire— with our multimeter, and see if the sensor reacts to engine intake airflow.

During the MAF signal test, here's what should happen:

• When we rev the engine up, airflow increases and the MAF signal voltage output should rise accordingly.
• When we release the throttle and engine RPMs drop, the MAF signal voltage should go down as airflow decreases.

No matter how many times we rev the engine and then let off the throttle, the MAF signal voltage output should always go up with engine RPM and come back down when it returns to base idle speed.

If the MAF sensor has failed on your Ford Escort or Mercury Tracer, the MAF signal voltage output will stay stuck at one value no matter how much we rev the engine up or down.

NOTE: The MAF sensor has to remain connected to its engine wiring harness connector. This means that to tap into the MAF signal wire, you're going to need a wire piercing probe. If you don't have one, this is the one that I use and recommend: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link)..

These are the test steps:

1. 1

   Switch your multimeter to Volts DC.

2. 2

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

3. 3

   Connect the red lead to the light blue with red stripe (LT BLU/RED) wire using a wire-piercing probe.
   
   This LT BLU/RED wire is labeled with the number 5 in the image above.

4. 4

   Start the engine and let it idle.
   
   Once idle smooths out, note the voltage reading on the multimeter. A little fluctuation is normal. This first reading is your base MAF signal voltage.

5. 5

   Rev the engine by opening the throttle.
   
   You can do this at the throttle body by moving the linkage, or by having a helper step on the accelerator pedal.

6. 6

   The MAF signal voltage should rise as RPM increases.

7. 7

   Release the throttle to let the RPM come back down.

8. 8

   The voltage should drop as the RPMs fall.

9. 9

   Repeat the accelerate/release cycle a few times to verify the results are consistent.

Let's take a look at what your test result means:

CASE 1: The signal voltage increased/decreased as you manually opened/closed the throttle. This result confirms that the MAF sensor on your Escort or Tracer is functioning correctly.

If the MAF sensor were defective, your multimeter who would've shown a voltage of value that would've stayed stuck at a specific number no matter how much you rev the engine.

CASE 2: The signal voltage DID NOT increase/decrease as you manually opened/closed the throttle. This isn't good. It could mean that the MAF sensor has failed or that it may not be getting power or Ground.

Before we condemn the MAF sensor as bad, we need to dig a little deeper. Head over to: TEST 2: Making Sure The MAF Is Getting VPWR.

TEST 2: Making Sure The MAF Is Getting VPWR

As you're probably already aware, your Escort or Tracer's MAF sensor is a hot wire type, and these hot wires need 12 Volts to be able to function.

In this test, we're going to make sure that they are getting the 12 Volts that they need. To do this, we'll disconnect the MAF sensor from its engine wiring harness connector.

Then with a multimeter, we'll check that the engine wire and harness connector's male terminal 2 has 10 to 12 Volts present with the key in the RUN position but with the engine OFF.

NOTE: The engine wiring harness MAF sensor connector has round male terminals, and resembles the one shown in the connector pinout illustration above.

Alright, these are the test steps:

1. 1

   Disconnect the MAF sensor from its engine wiring harness connector.

2. 2

   Put your multimeter in Volts DC mode.

3. 3

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

4. 4

   Gently probe round male terminal number 2 with the red multimeter lead.
   
   Terminal 2 should connect to the RED wire on the MAF sensor's engine wiring harness connector.

5. 5

   Turn the key to the RUN position, but don't crank or start the engine.

6. 6

   The multimeter should display 10 to 12 Volts.

Let's take a look at what your test result means:

CASE 1: The multimeter registered 10 to 12 Volts. This is the correct test result and tells you that the power circuit is OK.

The next step is to make sure that the MAF sensor is getting chassis Ground (PWR GND) from terminal 3. For this test go to: TEST 2: Making Sure The MAF Is Getting PWR GND (Chassis Ground).

CASE 2: The multimeter DID NOT register 10 to 12 Volts. This tells you that the MAP sensor is not getting power.

This test result also tells you that the MAF sensor is not the problem. Without juice (12 Volts) in this circuit, the mass airflow (MAF) sensor won't work.

Your next step is to find out why this VPWR power was missing and restore it.

TEST 3: Making Sure The MAF Is Getting PWR GND (Chassis Ground)

Now that you've confirmed that the MAF sensor's hot wires are getting VPWR, we need to confirm that they're also getting Ground.

This Ground is a chassis Ground and in Ford-speak it's known as the PWR GND Ground. Since this is a chassis Ground, it's available to the sensor at all times.

In other words, it doesn't matter what position the key is in (OFF, RUN, or START) his chassis Ground is available at terminal 3 at all times.

We'll do a simple multimeter voltage test at terminal 3 to make sure that the black (BLK) wire that connects to it is delivering a solid connection to chassis Ground.

This is what you'll do:

1. 1

   Unplug the MAF sensor from its engine wiring harness connector.

2. 2

   Set your multimeter to Volts DC.

3. 3

   Connect the red multimeter lead to the battery positive (+) terminal.

4. 4

   Probe round male terminal number 3 with the black multimeter lead.
   
   Terminal 3 should correspond to the BLK wire at the MAF sensor's engine wiring harness connector.

5. 5

   Your multimeter should show between 10 and 12 Volts.
   
   NOTE: Because this is a chassis Ground, it will always be present, whether the key is ON or OFF.

Let's take a look at what your test result means:

CASE 1: The multimeter registered 10 to 12 Volts. This test result tells you that the MAF sensor is getting Ground.

The next step is now to make sure that the MAF sensor is getting the MAF RTN Ground from the PCM. For this test go to: TEST 4: Making Sure The MAF Is Getting MAF RTN Ground.

CASE 2: The multimeter DID NOT register 10 to 12 Volts. This test result confirms that the MAF sensor is not getting the chassis Ground it needs to function.

You can also conclude that the MAF sensor is not the problem. Without a solid path to chassis Ground in this wire, the MAF sensor won't work. The next step is to find out why this chassis Ground is missing and restore it

TEST 4: Making Sure The MAF Is Getting MAF RTN Ground

Up to this point, your Escort or Tracer's MAF sensor diagnostic has revealed:

• The MAF signal output is stuck in one value, no matter the engine speed (TEST 1).
• The sensor is getting VPWR power (TEST 2).
• The sensor is getting PWR RTN chassis Ground (TEST 3).

For our final test, we're going to make sure that the PCM is providing the MAF sensor with a MAF sensor Ground.

This Ground is provided internally by the PCM and is known as the MAF RTN Ground.

To check for its presence at male terminal 4, we're going to do a simple multimeter voltage test on it. The wire that connects to terminal 4 is the tan with light blue stripe (TAN/LT BLU) wire of the connector.

NOTE: Since this Ground is provided internally by your vehicle's PCM, you've got to be careful not to connect 12V from the battery directly to this circuit, or you're going to fry the PCM. The multimeter voltage test I'm suggesting below is a safe way to check for the presence of this MAF RTN Ground at terminal 4.

Let's get started:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   Connect the red multimeter test lead to the battery positive (+) terminal.

4. 4

   Probe male terminal number 4 with the black multimeter test lead.
   
   Terminal number 4 should correspond to the TAN/LT BLU wire of the MAF sensor connector.

5. 5

   Turn the key to the RUN position but don't crank or start the engine.

6. 6

   You should see 10 to 12 Volts on the multimeter.

Let's take a look at what your test result means:

CASE 1: The multimeter registered 10 to 12 Volts. This is the correct test result and tells you that the fuel injection computer is providing Ground.

You can now conclude that the MAF sensor is toast and needs to be replaced, but only if you have confirmed the following:

• TEST 1 →The MAF signal voltage output is stuck in one value, no matter how much you rev the engine up or down.
• TEST 2 →You've confirmed that the RED wire is delivering VPWR (10 to 12 Volts).
• TEST 3 →Confirmed that the BLK wire is delivering PWR GND (chassis Ground).
• In this test section, confirmed the PCM is supplying the MAF RTN Ground to the sensor.

CASE 2: The multimeter DID NOT register 10 to 12 Volts. This test result confirms that the MAF sensor is not getting the Ground it needs to function (from the fuel injection computer).

You can also conclude that the MAF sensor is not the problem. Without this computer provided Ground, the MAF sensor will not work. The next step is to find out why this Ground is missing and restore it.

More 2.0L Ford Escort And Mercury Tracer Diagnostic Tutorials

You can find a complete list of 2.0L Ford Escort and Mercury Tracer tutorials in this index:

• 2.0L Ford Escort Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test Engine Compression (1997-2003 2.0L Ford Escort, Mercury Tracer).
• Common Causes Of Spark Plug Failure (1997-2003 2.0L Ford Escort, Mercury Tracer).
• How To Test For A Blown Head Gasket (1997-2003 2.0L Ford Escort, Mercury Tracer).
• How To Test The Throttle Position Sensor (1998-2003 2.0L Ford Escort ZX2).