How To Test The MAF Sensor (1990-1992 2.3L Ford Ranger)

This tutorial will help you test the mass air flow (MAF) sensor on the 1990-1992 2.3L Ford Ranger in four simple steps and with just a multimeter.

You don't need expensive diagnostic equipment like an automotive scan tool to test the MAF sensor.

You can find this tutorial in Spanish here: Cómo Probar El Sensor MAF (1990-1992 2.3L Ford Ranger) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 2.3L Ford Ranger: 1990, 1991, 1992.

NOTE: The following tutorials will help you test the MAF sensor on the 1993-1997 2.3L Ford Ranger:

• How To Test The MAF Sensor (1993-1994 2.3L Ford Ranger).
• How To Test The MAF Sensor (1995-1997 2.3L Ford Ranger).

Symptoms Of A Bad MAF Sensor

This is not an exhaustive list of symptoms, but covers most of the symptoms associated with a MAF sensor failure.

• MAF sensor diagnostic trouble codes that light up the check engine light (CEL) on your instrument cluster.
  • Code 26: MAF Out Of Self-Test Range.
  • Code 56: MAF Circuit Above Maximum Voltage.
  • Code 66: MAF Circuit Below Minimum Voltage.
  • Code 157: MAF Circuit Below Minimum Voltage.
  • Code 158: MAF Circuit Above Maximum Voltage.
  • Code 159: MAF Out Of Self-Test Range.
• MAF sensor malfunction that DOES NOT light up the check engine light (CEL).
• Lean or rich air-fuel mixture diagnostic trouble code.
• Fuel trim diagnostic trouble code.
• Lack of power when accelerating the engine under load.
• Black smoke coming from the tail-pipe.
• Bad gas mileage.
• Engine idles rough and stalls.

MAF Sensor Circuit Descriptions

The MAF sensor has four wires coming out of its connector. Each wire in the connector has a specific job to do.

Here's the description of each circuit:

Terminal	Wire	Description
D	Light blue with red stripe (LT BLU/RED)	MAF Signal
C	Tan with light blue stripe (TAN/LT BLU)	Ground (provided by PCM)
B	Black with white stripe (BLK/WHT)	Chassis Ground
A	Red (RED)	12 Volts

TEST 1: Making Sure The MAF Sensor Is Getting Power

The first test is to check that the MAF sensor is getting 12 Volts DC which are supplied by the red (RED) wire of the MAF sensor connector.

The RED wire connects to the terminal marked with the letter A in the photo above.

Once we have confirmed that the MAF sensor is receiving 12 Volts, we can move on to the next test.

NOTE: You won't be able to test the front of the terminal. To check for 12 Volts, 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

   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 RED wire of the MAF sensor connector.

4. 4

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

5. 5

   Turn the key ON 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 results mean:

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct result.

The next step is to make sure the MAF sensor has Ground, for this, go to: TEST 2: Making Sure The MAF Sensor Is Getting Chassis Ground.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. Recheck all of your multimeter connections and retest.

If you still do not see these 12 Volts, then this exonerates the MAF sensor as bad since without this voltage it will not function.

Your next step is to find out why these 12 Volts are missing and restore them to the RED wire.