This tutorial will help you test the mass airflow (MAF) sensor on the 1991-1994 3.0L V6 Ford Ranger.
All four MAF sensor tests detailed in this tutorial are performed using a multimeter, no scan tool is required.
Your test results will quickly help you to determine if the MAF sensor is good or bad.
Contents of this tutorial:
- Symptoms Of A Bad MAF Sensor.
- MAF Sensor Circuit Descriptions.
- TEST 1: Making Sure The MAF Sensor Is Getting Power.
- TEST 2: Making Sure The MAF Sensor Is Getting Chassis Ground.
- TEST 3: Making Sure The MAF Sensor Is Getting Ground (PCM).
- TEST 4: Testing The MAF Signal.
- More 3.0L Ford Ranger Tutorials.
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAF (1991-1994 3.0L V6 Ford Ranger) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 3.0L V6 Ford Ranger: 1991, 1992, 1993, 1994.
- 3.0L V6 Mazda B3000: 1994.
NOTE: The following tutorials will help you test the MAF sensor on the 1995-2001 3.0L Ford Ranger:
- How To Test The MAF Sensor (1995-1997 3.0L V6 Ford Ranger).
- How To Test The MAF Sensor (1998-2001 3.0L V6 Ford Ranger).
Symptoms Of A Bad MAF Sensor
The MAF sensor is monitored by the fuel injection computer when the engine is running.
If the MAF sensor fails, the fuel injection computer will register a MAF sensor diagnostic trouble code.
You'll see one of the following diagnostic trouble codes when the check engine light comes on:
- 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.
A bad MAF sensor will also cause engine performance issues. The following list, although not exhaustive, includes the most common symptoms you'll see:
- 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
MAF sensor connector illustration 1 of 2 belongs to the 1992-1994 3.0L Ford Ranger.
MAF sensor connector illustration 2 of 2 belongs to the 1991 3.0L Ford Ranger.
Both connectors have four wires and the following table has a brief description of each wire's function:
| 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 MAF sensor requires 12 Volts to operate, which are supplied by the red (RED) wire of the MAF sensor 4-wire connector.
The RED wire connects to the terminal marked with the letter A in the illustrations above.
For our first MAF sensor test, we'll check for 12 Volts on the red wire with a voltage test performed with a multimeter.
NOTE: Testing the terminal from the front of the connector is not possible with multimeter test leads. 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).
These are the test steps:
- 1
Disconnect the MAF sensor from its electrical connector.
- 2
Place your multimeter in Volts DC mode.
- 3
Connect the red multimeter test lead to the RED wire of the MAF sensor connector.
The RED wire connects to the terminal labeled with the letter A in the illustration above. - 4
Connect the black multimeter test lead probe the battery negative (-) terminal.
- 5
Turn the key ON but don't crank or start the engine.
- 6
You should see 10 to 12 Volts on the multimeter.
Let's interpret your test result:
CASE 1: The RED wire is supplying 10 to 12 Volts. This is the correct result.
The next step is to make sure the MAF sensor is receiving chassis Ground from the black with white stripe wire. Go to: TEST 2: Making Sure The MAF Sensor Is Getting Chassis Ground.
CASE 2: The RED wire IS NOT supplying 10 to 12 Volts. Without these 12 Volts the MAF sensor will not function.
This test result tells you that the MAF sensor itself is not faulty. Your next step is to find out why these 12 Volts are missing and restore them.
