How To Test The MAP Sensor (GM 2.4L Quad 4)

When the MAP sensor goes bad on your GM 2.4L Quad 4 equipped vehicle, you'll see one of the following codes stored in your vehicles memory: P0106, P0107, or P108.

The cool thing is that the manifold absolute pressure (MAP) sensor, on your vehicle, can easily be tested using only a multimeter. Not only that, it can be accurately tested so that you can say, "Yes, it's bad" or "NO", it's not bad".

Symptoms Of A Bad MAP Sensor

Your 2.4L Quad 4 vehicle's engine management system is a speed density type. In layman's terms this means that the fuel injection computer uses the following inputs to calculate the amount of air the engine is breathing:

• Engine RPM info provided by the crankshaft position sensor.
• Intake air temperature info provided by the intake air temperature (IAT) sensor.
• Intake manifold pressure info provided by the manifold pressure (MAP) sensor.

Since the MAP sensor is a very critical part of the engine management system, when it fails, your car's engine performance will take a nose-dive.

These are some of the symptoms your 2.4L Quad 4 GM car will experience with a bad MAP sensor:

1. The check engine light will be on with a MAP diagnostic trouble code (DTC) stored in the computer's memory.
2. If your 2.4L Quad 4 GM car is OBD II equipped, you'll see DTC P0106 or P0107 or P0108.
3. Your vehicle won't start or will have a long cranking time before it starts.
4. Black smoke coming out of the tailpipe along with really bad gas mileage.
5. The engine idles rough when running and has a lack of power when accelerated.

Where To Buy The MAP Sensor And Save

You can find the MAP sensor in just about any auto parts store, but I think you'll find the better price online. The following MAP sensors are pretty good deals:

Not sure if the MAP sensors in the links above fit your Quad 4 equipped car? Don't worry, once you get to the site they will ask you the specifics of your vehicle and make sure it fits. If it doesn't fit they will find you the right one.

MAP SENSOR TEST 1: Verifying The MAP Sensor Signal With A Multimeter

This first test will get the whole show on the road by first checking that the MAP sensor is producing a MAP signal or not. Depending on your results, you'll continue on to the next test or stop.

The instructions call for a vacuum pump. If you live here in the States and you don't have one, you can run down to your local AutoZone or O'Reilly Auto Parts and rent one for free. If this option is not available to you and you're itching to get started, you can use the good ole' lungs (in other words, attaching a vacuum hose to the MAP sensor vacuum inlet and sucking on the hose with your mouth).

NOTE: The MAP sensor must remain connected to its electrical connector to test its signal. You'll need to use a back probe on the connector or a wire piercing probe on the wire. You can see an example of this tool here: Wire Piercing Probe.

OK, this is what you need to do:

1. 1

   Remove the MAP sensor from the intake manifold.

2. 2

   Connect your vacuum pump to the MAP sensor's vacuum inlet. If you disconnected the MAP sensor, from its electrical connector to remove it from the intake manifold, reconnect it to it now.

3. 3

   Select Volts DC on your trusty multimeter.

4. 4

   Connect the red multimeter test lead to the wire labeled with number 2 (in photo above) with the appropriate tool.
   
   If you don't have a multimeter, take a look at my recommendation here: Buying A Digital Multimeter For Automotive Diagnostic Testing (at: easyautodiagnostics.com).

5. 5

   Connect the black multimeter test lead to the battery negative (-) terminal.

6. 6

   When all is ready, turn the key ON but don't start the engine. This supplies the MAP with power and Ground and your multimeter should register 4.7 Volts DC.

7. 7

   Apply vacuum to the MAP sensor with the vacuum pump (or your mouth). You should see following DC voltages at the following vacuum values if you're using a vacuum pump:
   
   1.) 0 in. Hg ...... 4.7 Volts.
   
   2.) 5 in. Hg ...... 3.9 Volts.
   
   3.) 10 in. Hg .... 3.0 Volts.
   
   4.) 20 in. Hg .... 1.1 Volts.
   
   Whether you're using a vacuum pump or the good ole' lungs, the important thing is that the voltage should increase and decrease without any gaps or skips on the multimeter. Repeat test steps 1 thru' 5 several times.

OK, let's take a look at what your vacuum pump test results mean:

CASE 1: The voltage increased and decreased smoothly and without gaps. This means that the manifold absolute pressure (MAP) sensor is good and not the cause of the MAP sensor code or problem on your GM 2.4L Quad 4. No further testing is required.

Now, if your vehicle still has the MAP sensor code lighting up the check engine on your instrument cluster, take a look at the section: The MAP Sensor Code Won't Go Away for more info.

CASE 2: Your multimeter registered some voltage, but not as indicated. This tells you that you have a bad manifold absolute pressure (MAP) sensor on your GM 2.4L Quad 4. Replacing the MAP sensor will solve the MAP code issue (P0106, P0107, P0108).

CASE 3: Your multimeter registered 0 Volts. This usually means that the MAP sensor is fried. But further testing is needed to be absolutely sure, I suggest confirming that the MAP sensor has power and Ground. If both (power and Ground) are present, the MAP is bad. To test for power, go to: MAP TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.