How To Test The MAP Sensor (1991-2000 3.0L Caravan, Grand Caravan, Voyager, Grand Voyager)

The manifold absolute pressure (MAP) sensor is a key component of the fuel injection system and plays an important role in determining the engine load by measuring the intake manifold vacuum. With this info, the fuel injection computer can determine how much air is entering the engine.

Sooner or later the MAP senor is gonna fail. If you're wondering how to test it, this tutorial will show you how. You'll only need a multimeter and a vacuum pump.

I'll walk you through three easy tests, and by the end, you'll be able to tell if your MAP sensor is functioning properly or if it's bad (and in need of replacement).

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L Chrysler Voyager: 1995.
• 3.0L Dodge Caravan: 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000.
• 3.0L Dodge Grand Caravan: 1992, 1993, 1994, 1995, 1996, 1997, 1988, 1999, 2000.
• 3.0L Plymouth Voyager: 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000.
• 3.0L Plymouth Grand Voyager: 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000.

What Does The MAP Sensor Do?

The manifold absolute pressure (MAP) sensor, is a small 3-wire component located on the passenger side of the intake manifold and mounted on a bracket in front of the alternator. Its main job is to check the air pressure (vacuum) in the intake manifold and send this information to the fuel injection computer.

When the fuel injection computer gets the air pressure readings from the MAP sensor, along with information from the CKP sensor (which measures engine speed or RPM) and the intake air temperature sensor, it can accurately determine the amount of air entering the engine. With this knowledge about the engine's air intake, the computer can then precisely calculate the right amount of fuel to inject into the engine's cylinders

To be a bit more specific:

• When you press the gas pedal, the throttle opens, letting more air into the manifold, and engine RPM increases.
• The vacuum pressure inside the intake manifold decreases (meaning the absolute pressure gets closer to atmospheric pressure).
• The MAP sensor sends this new info to the computer.
• The computer now knows more air is entering the engine and adjusts the amount of fuel to inject into the engine cylinders accordingly.
• When you release the gas pedal, the throttle closes, letting less air into the manifold, and engine RPM decreases.
• The vacuum pressure inside the intake manifold increases (meaning the absolute pressure becomes lower than atmospheric pressure).
• The MAP sensor sends this new info to the computer.
• The computer now knows less air is entering the engine and adjusts the amount of fuel to inject into the engine cylinders accordingly.

Symptoms Of A Bad MAP Sensor

When the MAP sensor stops working, the computer can't adjust the air/fuel mixture correctly. This mix is essential for the engine to run optimally, so, when it's not right, it'll lead to engine performance problems.

Here are some common symptoms you'll see that'll tell you the MAP sensor isn't working right:

• Check Engine Light: This malfunction indicator light will come on to warn you that something's wrong.
• MAP Sensor Trouble Codes (OBD I): If you're vehicle is equipped with OBD I, you'll have one of the following trouble codes stored in the computer's memory:
  • Code 14: Manifold Absolute Pressure (MAP) Circuit Low Voltage.
  • Code 14: Manifold Absolute Pressure (MAP) Circuit High Voltage.
• MAP Sensor Trouble Codes (OBD II): On OBD II equipped vehicles, you'll have one of the following trouble codes stored in the computer's memory:
  • P0105: MAP Circuit Malfunction
  • P0106: MAP/Barometric Pressure Circuit Range/Performance Problem
  • P0107: MAP Circuit Low Input
  • P0108: MAP Circuit High Input
• Poor Fuel Economy: The computer will be injecting too much fuel for the amount of air entering the engine, and you'll get less miles per gallon of fuel.
• Rough Idle: The engine may shake or vibrate when you stop, like at a red light.
• Engine Hesitation: When you step on the gas, the car may hesitate or jerk before picking up speed.
• Stalling: In severe cases, the car might stall out, especially when idling or at low speeds.

MAP Sensor Circuit Descriptions And Connector Pinout

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
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)	Sensor 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 released, its voltage signal increases.

To get the most accurate test result, you'll 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:

• Standard Motor Products AS26 Map Sensor (at: amazon.com)
• Spectra Premium MP120 Manifold Absolute Pressure Sensor (at: amazon.com)

TEST 1: Testing The MAP Sensor Voltage Signal

For our first test, we'll check the MAP sensor's signal voltage with a multimeter. Our goal is to observe how the sensor's signal changes when we manually apply and release a vacuum to it.

If the MAP sensor is OK, its voltage signal should decrease when we apply vacuum to it. Once we release the vacuum (we're applying to it), its voltage signal should increase back to its original value.

For this test, we'll use a vacuum pump but if you don't have one, don't worry. You can use your mouth to apply vacuum to the sensor with a vacuum hose.

We'll attach the multimeter to the wire that goes to the terminal labeled with the number 2 (as shown in the illustration above). This wire is the dark green with red stripe (DK GRN/RED) wire on 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. 1

   Remove the MAP sensor from its place on the intake manifold.
   
   NOTE: If you had to disconnect the MAP sensor to remove it, reconnect it now to its electrical connector.

2. 2

   Connect your vacuum pump to the MAP sensor's vacuum inlet port.

3. 3

   Set your multimeter's selector to Volts DC mode.

4. 4

   Connect the red multimeter test lead to the DK GRN/RED wire of the MAP sensor's connector.
   
   IMPORTANT: Remember, the MAP sensor must remain connected to its 3 wire connector.

5. 5

   Ground the black multimeter test lead directly on the battery negative (-) terminal.

6. 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. 7

   Now, apply vacuum to the MAP sensor with the vacuum pump (or your mouth). The voltage signal value should decrease.

8. 8

   Release the vacuum. Once released, your multimeter should show the original voltage value.

9. 9

   Apply and release vacuum to the MAP several times. Each time the voltage should decrease/increase 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 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.