TEST 3: Verifying The MAP Sensor Is Getting Ground
So far, your MAP sensor diagnostic has confirmed that:
One: The MAP sensor is NOT producing a decreasing/increasing voltage signal when you applied/released vacuum (TEST 1).
Two: That the DK GRN/RED wire of the MAP sensor's harness connector is supplying power (TEST 2).
The next step and the last one is to make sure that the MAP sensor is being fed Ground by the BLK/LT BLU (black w/ light blue stripe) wire of its harness connector.
IMPORTANT: The PCM is the one that provides this Ground internally, so be careful and don't intentionally or accidentally short this wire to battery voltage or you'll fry the PCM. The multimeter voltage test I'm suggesting the the test instructions is a safe way to test for the presence of Ground in the wire.
This is what you'll need to do:
Place your multimeter in Volts DC mode.
Disconnect the MAP sensor from its connector.
With the black multimeter test lead, probe the BLK/LT BLU wire that connects to the terminal labeled with the number 1 of the MAP sensor's harness connector.
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 red multimeter test lead directly to the battery's positive (+) terminal.
Turn the Key to the ON position (but don't start the engine).
If all is OK, your multimeter should read 10 to 12 Volts DC.
Let's take a look at your test results:
CASE 1: Your multimeter showed battery voltage. This is the correct test result and it means that the PCM is supplying Ground to the manifold absolute pressure (MAP) sensor.
This confirms that the manifold absolute pressure (MAP) sensor is bad and needs to be replaced. Why? Well, because so far you have confirmed that:
- The MAP sensor is not producing a signal when vacuum is applied to it (TEST 2).
- The MAP sensor is getting its 5 Volts (TEST 2).
- In this test step, you've confirmed that the MAP sensor is getting Ground.
Taking all of these 3 test results, you can conclude with confidence that you need to replace the MAP sensor with a new one.
CASE 2: Your multimeter did NOT show battery voltage. 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 10 to 12 Volts DC, then you've found the reason for the MAP sensor code/failure.
Without Ground in this circuit, the MAP sensor will not work. Now, it's beyond the scope of this article to test for this missing ground, but the most likely cause will be an ‘open’ between the PCM connector and the MAP sensor connector.
More 3.0L Chrysler Tutorials
You can find a complete list of tutorials in this index: Chrysler 3.0L Index Of Articles.
- How To Replace The Distributor (1988-2000 3.0L Chrysler).
- How To Test Engine Compression (1987-2000 3.0L Chrysler).
- How To Test The Throttle Position Sensor (1991-1995 3.0L Chrysler).
- How To Test For A Broken Timing Belt (1998-2000 3.0L SOHC Chrysler).
- Ignition Distributor System Tests 3.0L Chrysler, Dodge, Plymouth (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!