In this tutorial, I'm gonna' explain how to test the manifold absolute pressure (MAP) sensor with a multimeter and a vacuum pump.
All of the test steps are explained in a step-by-step manner. With your test results you'll be able to easily diagnose the MAP sensor as bad or good.
I'm also going to show you where you can buy the MAP sensor and save a few bucks.
This tutorial covers the following vehicles since they use the exact same MAP sensor: 2000, 2001, 2002, 2003 3.9L V6 Dodge Dakota.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAP (2000-2003 3.9L V6 Dodge Dakota) (at: autotecnico-online.com).
NOTE: This tutorial applies to the following vehicles since they use the exact same MAP sensor: 2000, 2001, 2002, 2003 3.9L V6 Dodge Dakota.
Symptoms Of A Bad MAP Sensor
The MAP sensor is one of three components that the fuel injection computer, on your 3.9L V6 Dodge Dakota, uses to find out the amount of air entering the engine.
In case you're wondering, the other two sensors are the crankshaft position sensor (for RPM input), and the intake air temperature sensor (for the intake air temperature input).
So when the MAP sensor fails, the engine in your Dodge Dakota is definitely going to resent it.
Since the MAP sensor input is monitored all the time, when it fails you're definitely going to see a MAP sensor diagnostic trouble code lighting up the check engine light. You'll see one of the following:
- DTC P0107 MAP Sensor Circuit Low Voltage.
- DTC P0108 MAP Sensor Circuit High Voltage.
You're also going to see one or more of the following symptoms:
- Rough idle.
- 'Rotten egg' smell coming from the exhaust.
- Won't pass the state mandated emissions test.
- Bad gas mileage.
- Lack of power, rough idle, or hesitation.
- Engine cranks a long time before starting.
MAP Sensor Circuit Descriptions
The MAP sensor is a 3 wire type sensor. This means that it has a power wire, a Ground wire and a signal wire. The table below has a brief description of each:
| Terminal | Wire | Description |
|---|---|---|
| 1 | ORG | 5 Volts |
| 2 | DK GRN/RED | MAP Signal |
| 3 | BLK/LT BLU | Ground |
The key to successfully diagnosing the MAP sensor as good or bad is to know that the MAP sensor reacts to vacuum that is being applied to it.
When the MAP sensor is powered up but it's not receiving vacuum, its voltage signal is around 4.5 to 4.7 Volts DC.
As vacuum is applied to the MAP sensor, it's voltage signal starts to decrease.
If the MAP sensor is bad, you'll notice that it's voltage signal does not decrease no matter the amount of vacuum that is applied to it.
Where To Buy The MAP Sensor And Save
The 2000-2003 3.9L V6 Dodge Dakota's MAP sensor isn't an expensive engine management component. The following links will help you to comparison shop and hopefully save you a few bucks on its purchase:
NOTE: The above manifold absolute pressure (MAP) sensor fits the following vehicles: 2000, 2001, 2002, 2003 3.9L V6 Dodge Dakota.
TEST 1: Testing The MAP Sensor Voltage Signal
To get our MAP sensor diagnostic on the road, the first thing that we're going to do is to make sure that the MAP sensor creates a voltage signal that decreases as vacuum is apply to it.
This test simply involves connecting a multimeter to the MAP sensor voltage signal wire and then manually applying vacuum to it with a vacuum pump.
The MAP signal wire is the dark green with red stripe (DK GRN/RED) wire of its 3-wire electrical connector. This wire is labeled with the number 2 in the photo above.
By the way, if you don't have a vacuum pump, no worries. You can use your mouth to apply vacuum to the sensor.
NOTE: If you don't have a vacuum pump you can use your mouth to apply vacuum to the MAP sensor. If you would like to buy a vacuum pump, check out this link: HTOMT 2 In 1 Vacuum Pump Test Set.
IMPORTANT: The manifold absolute pressure (MAP) sensor must remain connected to its electrical connector for this test to function properly. To be able to access the voltage inside the signal wire, you'll need to use either a back probe or a wire piercing probe. You can see an example of this tool here: Wire Piercing Probe.
Let's get started:
- 1
Remove the MAP sensor from the throttle body.
- 2
Connect your vacuum pump to the MAP sensor's vacuum inlet port.
NOTE: Reconnect the MAP sensor to its connector if you disconnected it. - 3
Place your multimeter in Volts DC mode.
- 4
Connect the red multimeter test lead to the DK GRN/RED wire of the MAP sensor's connector.
This wire is identified by the number 2 in the photo above.
Remember, the MAP sensor must remain connected to its 3 wire connector. - 5
Ground the black multimeter test lead directly on the battery negative (-) terminal.
- 6
Turn the key the ON position but don't start the engine. This will power up the MAP sensor and you should see a reading of 4.7 Volts DC on your multimeter.
- 7
Now, apply vacuum to the MAP sensor with the vacuum pump (or your mouth). The voltage signal value should decrease.
If you're using a vacuum pump: At 5 in.Hg → 3.9 Volts. At 10 in.Hg → 3 Volts. At 15 in.Hg → 2.1 Volts. At 20 in.Hg → 1.2 Volts. - 8
Release the vacuum. Once released, your multimeter should show the original voltage value.
Repeat this test step several times making sure that each time the voltage decreases/increases as you apply/release vacuum.
Let's examine your test:
CASE 1: The MAP voltage signal decreased and increased as you applied and released vacuum. This is the correct test result.
This test result confirms that the MAP sensor is working correctly (not defective). It also lets you know that the MAP sensor is getting 5 Volts and Ground.
CASE 2: The MAP voltage signal DID NOT decrease/increase as you applied and released vacuum. This test result usually indicates that the MAP sensor is defective.
To find out, the next step is to see if the orange (ORG) wire is feeding the MAP sensor with 5 Volts DC. For this test go to: TEST 2: Making Sure The MAP Sensor Has 5 Volts.
CASE 3: The multimeter DID NOT register any voltage. This test result usually indicates that the MAP sensor is defective.
To find out, the next step is to see if the orange (ORG) wire is feeding the MAP sensor with 5 Volts DC. For this test go to: TEST 2: Making Sure The MAP Sensor Has 5 Volts.
