You don't need a scan tool to test the MAF (Mass Air Flow) sensor on your Ford Escort (Mercury Tracer). This article will walk you through the whole process of testing and troubleshooting it using only a multimeter.
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 diagnosed in four easy steps.
If you're looking for the article on how to test the Ford MAF sensor that's not inside the air filter canister assembly, go here: How To Test Ford MAF Sensors Using A Multimeter.
Contents of this tutorial:
Puedes encontrar este tutorial en Español aquí: Cómo Probar El Sensor MAF De 2.0L Ford Escort, Mercury Tracer (en: autotecnico-online.com).
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:
- 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.
- MAF sensor malfunction that DOES NOT light up the check engine light (CEL).
- Lean and/or Rich code(s).
- Fuel trim code(s).
- A tremendous lack of power upon acceleration.
- Black smoke coming from the tail-pipe.
- Bad gas mileage.
- Vehicle may idle rough and stall.
Circuit Descriptions Of The Ford MAF Sensor's Connector
The mass air flow sensor on your Escort (or Tracer) may have 6 or 4 wires coming out of the plastic round air filter canister. If the MAF sensor has 6 wires, this indicates that the air temperature sensor is integrated within the sensor. If it's a 4 wire sensor, then the air temp sensor is located externally (usually on the air duct connecting the round air filter assembly to the throttle body).
Whether the MAF sensor's connector has 6 or 4 wires, they're tested in the exact same way! Here are the description of each circuit:
- Letter A:
- Power (12 Volts) Circuit.
- Letter B:
- Power Ground Circuit.
- Letter C:
- Sensor Ground Circuit (provided by PCM).
- Letter D:
- MAF Sensor Signal.
- Letter E:
- Air Temp Sensor Circuit (if applicable).
- Letter F:
- Air Temp Sensor Circuit (if applicable).
To test these circuits you'll need to use a tool to pierce the wire to be tested. I recommend using a wire-piercing probe since it'll be the most effective and easiest way of getting to the signal. If you need to see what this tool looks like, click here: Wire-Piercing Probe. Independent of the method you use, be careful not to damage the wire(s). Take all safety precautions.
Another important thing to note is that the color of the wires (coming out of your Escort or Tracer) does not matter. In other words, the circuit description/job of the wire is the same regardless of Make/Model and color of the wire.
IMPORTANT: All of the tests are ON CAR TESTS, do not remove the mass air flow sensor from the vehicle or from its plumbing.
How Does The MAF Sensor Work?
Knowing how the MAF sensor works on your Ford (or Mercury) car will help you to understand the tests you're about to perform. So here in a nutshell is what happens when the crank and start the car:
- The MAF sensor gets power (12 Volts) and Ground. Ground is provided by two different circuits. One Ground is provided directly by the battery negative terminal and the other one is provided by the PCM internally.
- When the engine finally starts and idles, the MAF sensor provides a voltage of about 1 Volt DC. This voltage may fluctuate a bit since it depends on the amount of air flow the engine needs to warm up and stuff.
- Now, as you accelerate the engine, the throttle opens. This lets more air into the engine.
- The MAF sensor senses this increase in air flow and increases the voltage signal to the PCM.
Now, just to recap the above info, the MAF signal's DC voltage is directly related to amount of air the engine is breathing. Therefore, if the engine is breathing in more air at 2500 RPM's that at an idle of 900RPM's the voltage output will be greater at 2500 RPM's than at idle.
Now, when testing this voltage signal, the important thing to know is not an actual Volts number at a specific RPM, but to make sure that the voltage signal increases as the engine is accelerated and that this voltage signal decreases as the engine returns to idle.
Any voltage value that does not correspond to the actual air intake (RPM's) of the engine indicates a bad MAF sensor. For example: You rev the engine up but the MAF signal voltage stays stuck in one number on the multimeter.
In the TEST 4 section of this article, I'll show how you'll use a base voltage reading at idle from the MAF sensor that will help you to confirm that the MAF sensor is bad or not.