This tutorial will show you a very accurate way to diagnose a manifold absolute pressure (MAP) sensor diagnostic trouble code P0108, P0109 or a BAD MAP sensor with a multimeter and a vacuum pump.
The MAP sensor diagnostic test is divided into three parts and all them are explained in detail.
Contents of this tutorial:
- Symptoms Of A BAD MAP.
- MAP SENSOR TEST 1: Checking The MAP Signal With A Multimeter.
- MAP SENSOR TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.
- MAP SENSOR TEST 3: Making Sure The MAP Sensor Is Getting Ground.
- MAP Code Will Not Go Away.
- How The MAP Sensor Works.
- Where To Buy The MAP Sensor And Save.
Also, this tutorial covers vehicles from Chrysler, Dodge, Plymouth, Eagle and Mitsubishi (2.0L, 2.4L, 2.5L, 3.3L, 3.8L). To see if this tutorial applies to your specific vehicle take a look at the Applies To container on the column on the left.
If you need the Chrysler 4 wire MAP sensor test, go here:
The following OBD II code tutorials will also help you diagnose your MAP sensor:
- P0107 MAP Sensor OBD II Trouble Code (at: troubleshootmyvehicle.com).
- P0108 MAP Sensor OBD II Trouble Code (at: troubleshootmyvehicle.com).
You'll find several Chrysler ‘How to Test’ tutorials by checking out the: Chrysler Index of Articles.
You can find this tutorial in Spanish here: Cómo Probar el Sensor MAP de Chrysler (de 3 Cables) (at: autotecnico-online.com).
Symptoms Of A BAD MAP Sensor
Your Chrysler's fuel system (and by extension, the ignition system), depend on the info that the MAP sensor feeds the fuel injection computer.
So, when the MAP sensor fails, you'll have the check engine light (CEL) shining nice and bright on your instrument cluster and sever engine performance problems. You'll see one (or more) of the following symptoms:
- MAP sensor diagnostic trouble code (DTC) P0107, P0108 stored in the vehicle's computer's memory.
- P0107: MAP Sensor Voltage Too Low. To learn more about DTC P0107, check out the following tutorial: P0107 MAP Sensor OBD II Trouble Code (at: troubleshootmyvehicle.com).
- P0108: MAP Sensor Voltage Too High. To learn more about DTC P0108, check out the following tutorial: P0108 MAP Sensor OBD II Trouble Code (at: troubleshootmyvehicle.com).
- BAD gas mileage.
- Black smoke coming out of the tail pipe, especially when you accelerate the vehicle.
- No power and/or hesitation as you accelerate the vehicle. It feels like all of a sudden someone cut the power out momentarily as you step on the gas to get the vehicle moving.
MAP SENSOR TEST 1: Checking The MAP Signal With A Multimeter
The manifold absolute pressure (MAP) sensor produces a DC voltage signal that varies according to the amount of engine vacuum present in the intake manifold. So the very first thing you'll do, is to verify that the MAP sensor is producing a healthy MAP signal that the PCM (Powertrain Control Module= Fuel Injection Computer) can use.
This is a pretty easy test and on which should take you about 15 minutes or less to do. If you don't own a vacuum pump, don't worry. You can apply vacuum to the MAP sensor with your mouth or you can rent one from your local AutoZone (or O'Reilly Auto Parts).
NOTE: You'll need a multimeter to test your vehicle's MAP sensor. If you don't have one and need to buy one or upgrade yours, the following recommendation will help: Abe's Digital Multimeter Recommendation.
IMPORTANT: The MAP sensor must remain connected to its electrical connector to read its voltage signal. You'll need to use a back-probe on the connector or a wire-piercing probe on the wire to access the MAP signal. You can see an example of this tool here: Wire Piercing Probe Review.
OK, let's start:
Remove the MAP sensor from the intake manifold. If you needed to disconnect the MAP sensor from it's electrical connector to remove it, reconnect it now (the MAP sensor must remain connected to its connector for this test).
Select Volts DC Mode on your multimeter and with the red multimeter test lead probe the wire identified by the number 3 in the photo.
The color of the wire may not be the same one as the one in the image viewer on your specific Chrysler (Dodge, Eagle, Plymouth, Mitsubishi) car or mini-van. This is nothing to worry about since you'll be able to test the correct circuit using the image as a guide.
Ground the black multimeter test lead on the battery negative (-) terminal.
Have your helper turn the Key On but don't start the engine.
You should see a voltage around 4.5 Volts DC registering on your multimeter. If it doesn't, don't worry about it just yet, continue with the other steps.
Connect your vacuum pump to the MAP sensor using a large diameter hose (I use a 3/8 fuel hose).
Whatever hose you use, it's important that it makes a tight seal on both the MAP sensor's vacuum inlet nipple and the vacuum hose.
Apply vacuum to the MAP sensor till the gauge's needle reaches 5 in. Hg of vacuum. These are the readings you should have as you pump the vacuum pump to different vacuum levels:
1.) 0 in. Hg ...... 4.7 Volts.
2.) 5 in. Hg ...... 3.9 Volts.
3.) 10 in. Hg .... 3.0 Volts.
4.) 15 in. Hg .... 1.1 Volts.
Release the vacuum you've applied. The voltage reading should go back down to the value you registered in step 5.
Let's take a look at what your test results mean:
CASE 1: As you applied vacuum, the voltage decreased in a smooth linear way with no gaps. This is the correct test result.
You can conclude that the manifold absolute pressure (MAP) sensor is working like it should and is not the cause of the issue. No further MAP sensor tests are needed.
Now, if the MAP sensor code won't go away, take a look at the info found at: MAP Code Will Not Go Away for a few more suggestions as to what could be causing the MAP sensor diagnostic trouble code (DTC).
CASE 2: As you applied vacuum, the voltage DID NOT decrease in a smooth linear way and/or there were gaps. This test results confirms that the MAP sensor is fried and that it needs to be replaced. Replacing the MAP sensor will solve the issue.
CASE 3: If the multimeter DID NOT register any voltage. This isn't good, but doesn't condemn the manifold absolute pressure (MAP) sensor as BAD yet.
The MAP sensor may not be getting a supply of either Power or Ground. To test this go to: MAP SENSOR TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.