How To Test The MAP Sensor (1991-1995 3.3L V6 Chrysler And Dodge Mini-Van)

In this tutorial, I'm gonna walk you through how to bench-test the MAP sensor on your 1990-1995 3.3L V6 equipped mini-van.

All you'll need is a multimeter and a vacuum pump —no worries if you don't own one, you can rent it from most auto parts stores like AutoZone or O'Reilly Auto Parts.

If you still can't get your hands on a vacuum pump —you can still get it done using your own lungs (yep, we'll cover that in the test steps).

Now, you might be thinking, "Why go through the trouble of testing the MAP sensor?" The reason is simple: a bunch of different problems can fool the fuel injection computer (th PCM or Powertrain Control Module) into throwing a MAP sensor code —even when the sensor itself is fine. That's why testing the MAP sensor off the engine is the way to go to know if it's actually toast or not.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.3L V6 Dodge Caravan: 1991, 1992, 1993, 1994, 1995.
• 3.3L V6 Dodge Grand Caravan: 1991, 1992, 1993, 1994, 1995.
• 3.3L V6 Plymouth Voyager: 1991, 1992, 1993, 1994, 1995.
• 3.3L V6 Plymouth Grand Voyager: 1991, 1992, 1993, 1994, 1995.

OTHER MAP SENSOR TESTS:

• How To Test The MAP Sensor (1996-2000 3.3L V6 Caravan, Grand Caravan, Voyager, Grand Voyager, Town & Country).
• How To Test The MAP Sensor (2001-2004 3.3L V6 Caravan, Grand Caravan, Voyager, Grand Voyager, Town & Country).

Symptoms Of A Bad MAP Sensor

When the manifold absolute pressure (MAP) sensor fails, the check engine light kicks on, and you'll see this diagnostic trouble code (DTC):

• Code 14: MAP Sensor Voltage Too Low or Too High.

But the trouble doesn't stop with just a code. Your 3.3L V6 mini-van isn't gonna run right. You'll notice one —or maybe several— of the following symptoms:

• Rough idle: The engine runs uneven or shaky while idling.
• Black smoke: You'll see black smoke coming out the tailpipe.
• Engine stalls under load: The moment you shift into Drive (which loads the engine), it shuts off.
• Engine dies right after starting: This one's pretty common.
• Lack of power: You'll feel it when trying to accelerate down the road —it just doesn't pull like it should.

MAP sensors do fail on their own, but it's also common for another engine problem to trick the PCM (Powertrain Control Module, your van's fuel injection computer) into thinking the MAP sensor's at fault.

If you really wanna know if the MAP sensor's bad —without guessing or replacing it blindly —you need to test it off the engine. The method I'm about to show you is exactly that: a MAP sensor bench test.

If after doing the MAP sensor test and the MAP sensor is good, then take a look at the section:

• MAP Sensor Code Won't Go Away.

How The MAP Sensor Works

Your 3.3L V6 mini-van runs on what's called a "speed density" fuel system. That means it doesn't use a mass air flow (MAF) sensor to figure out how much air the engine's pulling in.

Instead, the PCM relies on:

• The MAP sensor to read engine vacuum.
• The crankshaft position (CKP) sensor to track RPMs.
• The IAT sensor to measure the temp of the air the engine is breathing.

With the input of these three sensors, it calculates how much air is entering the engine.

Here's what happens when you turn the key and fire up the engine:

• MAP sensor gets activated: The PCM sends:
  • 5 Volts to the MAP sensor through the terminal marked number 3.
  • Ground, also from the PCM, through the terminal marked number 1.
• Reading engine vacuum: Once it's powered, the MAP sensor starts measuring how much vacuum the engine is producing.
• Sending data to the PCM: The vacuum reading travels back to the computer through the middle wire of the connector, which corresponds to the terminal labeled number 2.
• Fuel control kicks in: Using data from the MAP sensor, the IAT sensor, and the CKP sensor, the PCM figures out the right air-fuel mixture. It then:
  • Adjusts injector pulse width —that's how long the fuel injectors stay open.
  • Tweaks ignition timing.

The MAP sensor plays a big role in keeping your 3.3L Chrysler/Dodge/Plymouth mini-van running right. So with that covered, let's get into the testing part.

Where To Buy The MAP Sensor And Save

The following links will help you comparison shop for the MAP sensor:

Not sure if the above MAP sensor fits your particular mini-van? Don't worry. Once you get to the site they'll make sure it fits. If it doesn't, they'll find you the right one.

TEST 1: Verifying The MAP Signal

The first thing we're gonna do is check if the MAP sensor is capable of producing a variable signal as we apply vacuum to it.

If the sensor is good, it's voltage output signal should decrease when we apply vacuum and increase when we release the vacuum.

If the MAP sensor is toast, it's voltage signal will not change no matter the amount of vacuum we apply.

NOTE: Need a multimeter or a vacuum pump (or thinking about upgrading)? These are the exact ones I personally use and recommend:

• Multimeter: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter with NCV Feature, Mastech MS8268 Upgraded, MS88 (at: amazon.com).
• Vacuum pump: HTOMT 2 In 1 Vacuum Pump Test Set (at: amazon.com).

Alright, here's how to get started:

1. 1

   Take the MAP sensor off the intake manifold.

2. 2

   Hook up the MAP sensor to your vacuum pump. Make sure the vacuum hose fits snugly on both the pump and the sensor's vacuum port.
   
   I used an old spark plug wire boot to bridge the connection between the vacuum pump and the MAP sensor (see photo 2 of 2 in the image viewer above).

3. 3

   Attach the black lead of your multimeter to the battery's negative (-) terminal.

4. 4

   Set your multimeter to read DC Volts.

5. 5

   Take the red lead from your multimeter and tap into the middle wire of the connector using the right probing tool.
   
   IMPORTANT: Don't unplug the MAP sensor —it must stay connected to the 3-wire plug.
   
   NOTE: You can use a back probe or a wire-piercing tool for this connection. Need help? See Wire Piercing Probe for details.

6. 6

   Turn the ignition key to the ON position, but don't start the engine.
   
   This powers up the MAP sensor with 5 Volts straight from the PCM (Powertrain Control Module = Fuel Injection Computer).

7. 7

   With the Key On Engine Off (KOEO) and no vacuum applied, your multimeter should read around 4.5 to 5 Volts DC.

8. 8

   Start applying vacuum using the vacuum pump (or your mouth).

9. 9

   Your multimeter should show a drop in voltage. The voltage can drop down to around 1.5 Volts or less (depending on the amount of vacuum you apply).

10. 10

    Release the vacuum.

11. 11

    The voltage should jump back up to the 4.5–5 Volt range.

12. 12

    Repeat steps 8 thru 11 a few times.
    
    You should get the same voltage drop and rise each time you apply and release vacuum.

Now let's break down what your results actually mean:

CASE 1: Your multimeter showed a steady drop in voltage as you applied vacuum. That's your confirmation that the MAP sensor's working like it should. No need for more tests.

If you're still seeing a MAP sensor code lighting up the check engine light, check out this next section: MAP Sensor Code Won't Go Away.

CASE 2: Your multimeter didn't show any drop in voltage when you applied vacuum. That generally means your MAP sensor is faulty and needs to be replaced.

To make sure it's toast, we need to make sure it's getting power and Ground. For the first of these two tests, go to: TEST 2: Making Sure The MAP Sensor Is Getting Power.

CASE 3: Your multimeter didn't register any voltage at all. This usually points to a dead MAP sensor.

But to be sure, we need to confirm that it's actually getting both power and Ground. Head over to: TEST 2: Making Sure The MAP Sensor Is Getting Power.

TEST 2: Making Sure The MAP Sensor Is Getting Power

If you've made it here, it's because in TEST 1, you confirmed that your 3.3L V6 mini-van's MAP sensor isn't producing a variable voltage signal (when you apply/release vacuum to it).

The next step is to check if the MAP sensor's actually getting power. Without power, it won't function at all.

The PCM (Powertrain Control Module = fuel injection computer) sends out a steady 5 Volts to power the sensor and is delivered by the wire that connects to female terminal 3 (see the illustration of the front of the connector above).

Here's what you need to do next:

1. 1

   Unplug the MAP sensor from its 3-wire connector.

2. 2

   Connect the black lead of your multimeter to the negative (-) battery post.

3. 3

   Set your multimeter to DC Volts mode.

4. 4

   Turn the ignition key to the ON position, but don't start the engine.

5. 5

   Use the red test lead to probe the front of the terminal marked number 3 (see illustration above).

6. 6

   You should see a reading between 4.5 and 5 Volts DC on your multimeter.

Now let's break down the results:

CASE 1: You saw 4.5 to 5 Volts on the multimeter. That's the correct voltage. It means the MAP sensor is getting power.

Now we still need to make sure the MAP sensor is also getting Ground. Head over to this next section: TEST 3: Making Sure The MAP Sensor Is Getting Ground.

CASE 2: You didn't see 4.5 to 5 Volts on the multimeter. Double-check your test connections.

If you still don't see the 4.5 to 5 Volts, the MAP sensor isn't the problem —because it can't work at all without that power supply.

Troubleshooting the issue behind these missing 5 Volts is beyond the scope of this tutorial, but at least you've ruled out the MAP sensor itself.

Once you fix the issue that's keeping the sensor from getting power, your MAP-related problems on your 3.3L V6 mini-van should be resolved.