TEST 2: Verifying The MAP Sensor Is Getting Power
Your vehicle's PCM is the one that supplies power to the MAP sensor. This power is in the form of 5 Volts DC and it reaches the MAP sensor thru' the violet with white stripe (VIO/WHT) wire of the MAP sensor electrical connector.
To confirm that the MAP sensor's getting power, all we need to do is a simple multimeter voltage test.
These are the steps:
With your multimeter still in Volts DC mode from the previous test and the key on (but engine off).
Probe the VIO/WHT wire that connects to the MAP sensor connector terminal labeled with the #1, in the illustration above, with the RED multimeter 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.
Now ground the multimeter's BLACK test lead on the battery's negative post.
Your multimeter should register 4.5 to 5 Volts DC on its display.
Let's take a look at what your results mean:
CASE 1: The VIO/WHT wire is feeding the MAP sensor 4.5 to 5 Volts DC: 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 MAP Is Getting Ground.
CASE 2: The VIO/WHT wire IS NOT feeding the MAP sensor 4.5 to 5 Volts DC: Double check your test connections and make sure that the key is in the On position (to power up the connector).
If your multimeter still doesn't register these 4.5 to 5 Volts DC, then this lack of power is behind the MAP sensor not working. Without power the MAP sensor will not create a MAP voltage signal.
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 2.7L equipped Dodge/Chrysler.
TEST 3: Verifying The MAP Sensor Is Getting Ground
The PCM also supplies the MAP sensor with ground and it does this thru' the black with light blue wire (BLK/LT BLU) of the MAP sensor's engine wiring harness connector.
This ground can be verified in one of several ways. What we'll do is a safe and simple multimeter voltage test.
IMPORTANT: Be careful NOT to short the BLK/LT BLU wire, accidentally (or intentionally), to battery power or you will fry the PCM. Doing a voltage test with a multimeter, as described in the test steps below, is a safe way to test the BLK/LT BLU wire.
These are the steps:
With your multimeter still in Volts DC mode from the previous test and the Key On (but engine Off).
Probe the BLK/LT BLU wire with the BLACK multimeter lead.
It doesn't matter if you probe this circuit (wire) with the connector connected to the MAP sensor or not, but do not probe the front of the connector (if you decide to unplug the connector to test for this path to ground).
Now connect the multimeter's RED test lead on the battery's positive (+) Post.
Your multimeter should register 10 to 12 Volts DC on its display.
OK, let's take a look at what your results mean:
CASE 1: The multimeter showed 12 Volts, thus confirming the BLK/LT BLU wire is feeding ground to the MAP sensor: This is the correct test result and it means that the manifold absolute pressure (MAP) sensor is being fed with ground by the PCM.
Taking into account all of your MAP sensor test results till this point, you can confidently conclude that the MAP sensor is fried and needs to be replaced.
Here's why: In MAP sensor TEST 1 and 2, you verified that the MAP sensor is not producing the correct values (when you applied vacuum) and that it does have power. Since in this test step you have confirmed that the MAP sensor does have a solid path to ground, these results, interpreted together, indicate that the MAP sensor is BAD.
CASE 2: The multimeter DID NOT show 12 Volts, thus confirming the BLK/LT BLU wire IS NOT feeding ground to the MAP sensor: Double check that you're testing the BLK/LT BLU wire and repeat the test.
If your multimeter still DOES NOT show 12 volts, then this lack of ground is behind the MAP sensor issue and trouble code. This test result also exonerates the MAP sensor itself as bad.
Here's why: Without a good path to ground, that the PCM provides internally, the MAP sensor will not work. With this test result, you have eliminated the MAP sensor as BAD.
Although it's beyond the scope of this tutorial, you'll need to restore this missing ground to get the MAP sensor issue (and trouble code) to go away.