When the MAP sensor goes BAD on your GM 2.4L Quad 4 equipped vehicle... you 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".
This article is broken up into several different parts and so to help you navigate it a little easier, here are its contents at a quick glance:
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:
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:
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).
OK, this is what you need to do:
Remove the MAP sensor from the intake manifold.
Connect your vacuum pump to the MAP sensor's vacuum nipple. If you disconnected the MAP sensor, from its electrical connector to remove it from the intake manifold... reconnect it to it now.
Select Volts DC on your trusty multimeter and probe the wire labeled with number 2 (in photo above).
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).
The BLACK multimeter test lead needs to be grounded, preferably on the battery negative terminal.
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.
Now, 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: MAP 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: Verifying the 5 Volt Reference Supply.
“A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.”