TEST 1: Checking For The MAP Sensor Signal
In this first test, we're gonna' bench-test the MAP sensor by manually applying vacuum to it and while it's still connected to its electrical connector (but with the engine off).
You'll tap into the DK GRN/RED (dark green w/ red stripe) wire of the MAP sensor's engine harness connector (since this is the wire that carries the MAP signal to the PCM) with your multimeter and see if the voltage signal increases/decreases as you apply and release vacuum to the MAP sensor's vacuum port.
NOTE: Although the instructions assume you're using a vacuum pump, if you don't have one, you can use your mouth and a vacuum hose to apply vacuum to the MAP sensor's vacuum port.
IMPORTANT: The MAP sensor must remain connected to its electrical connector to test its MAP signal voltage. 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 and where to buy it here: Wire-Piercing Probe.
OK, this is what we'll do:
Remove the MAP sensor from the intake manifold (if you need to gain access to its vacuum port).
Once you have removed it, reconnect it back to its electrical connector.
Select Volts DC on your multimeter.
Probe the middle wire of the MAP sensor with the red multimeter test lead.
This is the wire that connects to the MAP sensor engine harness connector's terminal labeled with the number 2 in the photo above.
Connect the black multimeter test lead on the battery's negative (-) terminal.
Now, connect your vacuum pump to the MAP sensor.
Turn the Key to the ON position (don't start the engine).
With the key On and no vacuum applied to the MAP sensor your multimeter should display around 4.5 to 4.8 Volts DC.
Apply vacuum. As you apply vacuum, your multimeter should read:
1.) 5 in Hg - 3.9V.
2.) 10 in Hg - 3.1V.
3.) 15 in Hg - 2.1V.
NOTE: If you're using your mouth to apply vacuum to the MAP sensor, you're not gonna' be able to get the MAP voltage down to 2.1 V (or less) and this is normal (since you won't be able to produce that much suction/vacuum without a vacuum pump). What's important is for the voltage to decrease and increase as you apply and release vacuum to the sensor.
CASE 1: The MAP sensor's voltage decreased/increased as you applied/released vacuum- This tells you that the MAP sensor is OK and not defective.
This test result also confirms that your 3.0L Chrysler car or mini-van's MAP sensor is getting power (5 Volts) on the VIO/WHT wire and Ground on the BLK/LT BLU wire.
CASE 2: The MAP sensor's voltage DID NOT decrease/increase as you applied/released vacuum- 9 times out of 10 this test result usually means that the MAP sensor is bad but just to make sure, we need to confirm that the MAP sensor is getting both power and Ground.
For the next step, go to: TEST 2: Checking That The MAP Sensor Is Getting Power.
TEST 2: Checking That The MAP Sensor Is Getting Power
So far, you have confirmed that the MAP sensor is not producing a decreasing/increasing MAP signal as you apply/release vacuum to it...
... to make sure that the MAP sensor is bad, we now need to make sure it's getting power on the VIO/WHT (violet w/ white stripe) wire of the MAP sensor harness connector.
The VIO/WHT wire is the one that connects to the terminal labeled with the number 3 in the illustration in the image viewer above.
This is what you'll need to do:
Place your multimeter in Volts DC mode.
Disconnect the MAP sensor from its connector.
With the red multimeter test lead, probe the wire labeled with the number 3.
Avoid probing the front of the connector to avoid damaging the female metal terminal.
The best way to get to the signal inside the wire is using a Wire Piercing Probe (to see what this tool looks like, click here: Wire-Piercing Probe).
Connect the black multimeter test lead directly on the battery's negative (-) terminal.
Turn the Key to the ON position (but don't start the engine).
If all is OK, your multimeter should read 4.5 to 5 Volts DC.
Let's take a look at your test results:
CASE 1: 4.5 to 5 Volts are present. So far so good, since this means that the PCM is supplying power to the manifold absolute pressure (MAP) sensor.
The next step is to make sure that the PCM is feeding your 3.0L Chrysler's MAP sensor with ground. For this test, go to: TEST 3: Verifying The MAP Sensor Is Getting Ground.
CASE 2: 4.5 to 5 Volts ARE NOT present. Recheck your multimeter connections and retest.
If after checking all of your multimeter connections and making sure the Key is in the ON position AND your multimeter does not register the 4.5 to 5 Volts DC, then you've found the reason for the MAP sensor code/failure.
Without power in this circuit, the MAP sensor will not work. Now, it's beyond the scope of this article to test for this missing Voltage, but the most likely cause will be an ‘open’ or a short between the PCM connector and the MAP sensor connector.