TEST 1: Verifying The MAP Signal
The very first thing we'll do is remove the MAP sensor from the throttle body to bench test it.
Although you're gonna' remove the MAP sensor, you'll leave it connected to its electrical connector and then apply vacuum to it. This will verify whether the MAP sensor on your Dodge pick up (or van or SUV) is fried or not.
The instructions call for a vacuum pump. If you don't have one and you live here in the States, you can run down to your local Auto Zone or O'Reilly Auto Parts and rent one for free.
If you can't get your hands on a vacuum pump and you're itching to get started, you can use the good ole' lungs and mouth.
NOTE: You can use an analog or a digital multimeter for this test. If you don't have a multimeter or need to upgrade yours, check out my recommendation here: Buying A Digital Multimeter For Automotive Diagnostic Testing (at: easyautodiagnostics.com).
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 inlet nipple. Remember, the MAP sensor has to remain connected to its connector (this so that the PCM can power it up with voltage and ground).
Place your multimeter in Volts DC mode and probe the wire labeled with number 2 (in the image viewer).
NOTE: Since the MAP sensor needs to remain connected to its harness connector, you'll need to either back-probe the connector or use a wire piercing probe to get to the signal inside the wire (to see what a wire piercing probe looks like: Wire Piercing Probe Tool).
Connect the black multimeter test lead needs to 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 your mouth (to apply vacuum), the voltage on your multimeter 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 confirms that the MAP sensor on your Dodge pick up (or SUV or van) is OK and NOT the cause of the problem.
Now, if the PCM is still lighting up the check engine light with a MAP sensor diagnostic trouble code, 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 the MAP sensor is fried and needs to be replaced. Replacing the MAP sensor will solve the MAP code issue (P0106, P0107, P0108)
CASE 3: Your multimeter registered 0 Volts. This could mean several things. So further testing is necessary. The next steps (tests) are to make sure that the MAP sensor has power and Ground. If both (power and Ground) are present, the MAP sensor is bad. To test for power, go to: MAP TEST 2.
TEST 2: Making Sure That The MAP Sensor Is Getting Power
So far, you know that the MAP sensor is not creating a signal. The next test is to make sure that the MAP sensor is getting power, since without power it won't work.
The PCM (Powertrain Control Module = fuel injection computer) is the one that supplies the MAP sensor with power. And this power comes in the form of 5 Volts DC.
Since this circuit is directly connected to the PCM, be careful and don't 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 1, 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.
Now Ground the black multimeter test lead on the battery's negative post.
Your multimeter should show you either:
1.) 5 Volts DC
2.) 0 Volts.
OK, now that the testing part is done, let's take a look at what your results mean:
CASE 1: The multimeter registered 5 Volts. So far so good (since this is the correct test result), now you need to check that the MAP sensor is getting Ground. For the Ground test, go to: MAP SENSOR TEST 3.
CASE 2: The multimeter DID NOT register 5 Volts. Recheck all of your connections and retest. If still now voltage, this tells you that this lack of voltage is the reason the MAP sensor is not producing a 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 Dodge pick up (or van or SUV).