TEST 1: Verifying The MAP Signal
The very first thing you need to do, is remove the MAP sensor from the intake manifold (remember, we're gonna' bench test it).
Once removed, reconnect it to its electrical connector, since we'll let the PCM power it up for us (while we test it).
The next step will to see if the MAP sensor is able to create a good MAP signal. This is done using a vacuum pump while the MAP sensor is still connected electrically to the vehicle.
If you don't have a vacuum pump, you have two options: 1.) Rent one from AutoZone or O'Reilly Auto Parts or 2.) Use your mouth to suck on the MAP sensor via a vacuum hose (using the good ole' lungs is not the most accurate way, but it does work).
OK, to get this show on the road, this is what you need to do:
Remove the MAP sensor from its spot on the intake manifold.
Connect the MAP sensor to the vacuum pump. The vacuum hose that you need to use has to fit tightly around both the vacuum pump and MAP sensor's vacuum port.
I used a spark plug wire boot that I removed from an old spark plug wire to connect my vacuum pump to the MAP sensor (see photo 2 of 2 in the image viewer above).
Set your multimeter to Volts DC mode and with the red multimeter test lead, pierce the wire labeled with the number 1 in the image viewer.
Remember, the MAP sensor must remain connected to its 3 wire connector.
Connect the black multimeter test lead directly to the battery negative post.
Turn the key on but don't start the engine. This will enable the manifold absolute pressure (MAP) sensor to get power in the form of 5 Volts from the PCM (Powertrain Control Module= Fuel Injection Computer).
With the Key On Engine Off (KOEO) and without any vacuum applied to the MAP sensor your multimeter should register about 4.5 to 5 Volts DC.
Now, as you pump up the vacuum pump, the MAP sensor should make your multimeter register a decreasing voltage that can go as low as 1.5 Volts or less.
Repeat this test step several times and each time, you should see the same values on your multimeter.
If you're using your mouth to apply vacuum to the MAP sensor, then what you should see is the voltage decrease.
When you stop and release whatever vacuum you created with the good ole' lungs, the MAP voltage should go up to about 4.5 to 5 Volts.
OK, let's take a look at what your results mean:
CASE 1: Your multimeter displayed a decreasing voltage signal as you pumped up the vacuum. Your multimeter test results confirm that the manifold absolute pressure (MAP) sensor is OK and working like it should. 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 Sensor Code Won't Go Away for more info.
CASE 2: Your multimeter DID NOT display a decreasing voltage signal as you pumped up the vacuum gauge. This confirms that the manifold absolute pressure (MAP) sensor on your 3.3L V6 Chrysler (Dodge) mini-van is bad and needs to be replaced. Replacing the MAP sensor will solve the issue.
CASE 3: Your multimeter DID NOT register any voltage. This usually means that the MAP sensor is fried. 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: TEST 2: Verifying The MAP Sensor Has Power.
TEST 2: Verifying The MAP Sensor Has Power
You've reached this point, because in TEST 1, you have confirmed that the MAP sensor on your Chrysler 3.3L mini-van is not creating a MAP signal or the MAP signal is erratic
The next test step is to verify that the MAP sensor is getting power, since without power it won't work. This power come in the form of 5 Volts and the PCM (Powertrain Control Module = Fuel Injection Computer) is the one that provides this juice.
One word of caution, since the PCM is the one that feeds these 5 Volts to the MAP sensor, you've got to be careful not to short this wire to battery power (12 Volts), or you run the risk of frying the PCM.
Alright, this is what you'll need to do:
With your multimeter still in Volts DC mode from the previous test and the Key On (but Engine Off).
Probe the wire labeled with the number 3, in the image viewer, with the red multimeter test lead.
You can test for these 5 Volts with the MAP sensor's electrical connector connected to the MAP sensor or not. Just avoid probing the front of the connector.
Ground the black multimeter test lead on the battery's negative post.
Your multimeter should register 4.5 to 5 Volts DC.
Let's take a look at what your results mean:
CASE 1: The multimeter registered 5 Volts. This is the correct result and it's starting to look like the MAP sensor is bad but you still need to check that the MAP sensor is getting Ground. For the Ground test, go to: TEST 3: Verifying The Ground Circuit.
CASE 2: The multimeter DID NOT register 5 Volts. This results lets you know that the MAP sensor is not bad, since without these 5 Volts DC, the MAP sensor can not function.
Although it's beyond the scope of this article to troubleshoot the cause of these missing 5 Volts, you have now eliminated the MAP sensor as bad. Resolving the issue that is keeping these 5 Volts from being supplied will solve the MAP sensor issue on your 3.3L equipped Chrysler mini-van.