Testing the manifold absolute pressure (MAP) sensor is not difficult. It can be tested with 3 simple tests and these are done with a multimeter. You don't need a scan tool!
In this tutorial I'll explain it all in a step-by-step way. You'll be able to easily find out if the MAP sensor is bad or not.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAP (1991-1995 2.5L Caravan y Voyager) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 2.5L Dodge Caravan: 1991, 1992, 1993, 1994, 1995.
- 2.5L Plymouth Voyager: 1991, 1992, 1993, 1994, 1995.
Symptoms Of A Bad MAP Sensor
The fuel injection system, of your vehicle's 2.5L engine, is a 'speed-density' type.
This means that the fuel injection computer needs to know 3 things to calculate the amount of air entering the engine. These 3 things are: intake air temperature, engine load (engine manifold vacuum), and engine speed (RPM).
It's the manifold absolute pressure (MAP) sensor that provides the engine load information to the fuel injection computer.
Since the MAP sensor is a critical engine management component, when it fails you'll see the check engine light lit up with a MAP sensor trouble code:
- Code 14: MAP Sensor Voltage.
You're also gonna' see one or more of the following symptoms:
- Engine is difficult to start.
- Rough engine idle.
- Black smoke coming out if the tail pipe when engine is running.
- Lack of power when accelerating the engine or vehicle down the road.
The MAP sensor is 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:
| MAP Sensor Circuits 1991-1995 | ||
|---|---|---|
| Terminal | Wire | Description |
| 1 | Violet with white stripe (VIO/WHT) | 5 Volts |
| 2 | Dark green with red stripe (DK GRN/RED) | MAP Signal |
| 3 | Black with light blue stripe (BLK/LT BLU) | Ground |
To successfully test the manifold absolute pressure (MAP) sensor, it's important to know that:
- As vacuum is applied to the MAP sensor, its voltage signal decreases.
- As this vacuum is relaesed, its voltage signal increases.
To get the most accurate test result, from the MAP sensor test, I'll have you apply vacuum to it with a vacuum pump. If you don't have one, don't worry. You can use your mouth.
Where To Buy The MAP Sensor And Save
The MAP sensor isn't an expensive engine management component, but it never hurts to save a few bucks and so with that in mind I think that the following links will help you to comparison shop for it and maybe even save a few bucks:
NOTE: If you're not sure if the above MAP sensor fit your particular 2.5L Dodge Caravan (Plymouth Voyager) don't worry, once you get to the site, they'll make sure the sensor is the right one, if not, they'll find you the right one.
TEST 1: Testing The MAP Sensor Voltage Signal
The first thing we're gonna' do is to test the MAP sensor's signal voltage with a multimeter.
We'll connect the multimeter to the wire labeled with the number 2 (in the photo above).
This wire is the green with red stripe (GRN/RED) wire of the connector.
If you don't have a multimeter and need to buy one, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing (at: easyautodiagnostics.com).
IMPORTANT: The MAP sensor needs to stay connected to its electrical connector for this test to work. You'll need to use a back-probe or a wire-piercing probe to measure the MAP signal voltage. To see what a wire-piercing probe looks like, go here: Wire Piercing Probe.
Let's get started:
- 1
Disconnect the MAP sensor from its vacuum hose. Don't remove the MAP sensor from its place.
- 2
Connect your vacuum pump to the MAP sensor's vacuum inlet port. Reconnect the MAP sensor to its connector if you disconnected it.
- 3
Set your multimeter's selector to Volts DC mode.
- 4
Connect the red multimeter test lead to the GRN/RED wire of the MAP sensor's connector.
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
When everything is ready, turn the key to 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.
- 8
Release the vacuum. Once released, your multimeter should show the original voltage value.
- 9
Apply and release vacuum to the MAP several times. Each time the voltage decreases/increases as you apply/release vacuum.
Let's find out what your test results mean:
CASE 1: The MAP voltage signal decreased and increased as you applied and released vacuum. This is the correct and expected test result and lets you know that the MAP sensor on your 2.5L Dodge Caravan (Plymouth Voyager) is not defective.
This test result also let you know that the MAP sensor is getting power and Ground from the fuel injection computer.
CASE 2: The MAP voltage signal DID NOT increase (and/or decrease) as you applied and released vacuum. In most cases, this test result is enough to confirm that the MAP sensor is defective and that it needs to be replaced.
But to be sure that the MAP sensor is defective, we need to make sure that it's getting power and Ground. For these two tests go to: TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.
CASE 3: The multimeter DID NOT register any voltage. In most cases, this test result is enough to confirm that the MAP sensor is defective and that it needs to be replaced.
But to be sure that the MAP sensor is defective, we need to make sure that it's getting power and Ground. For these two tests go to: TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.
