How To Test The MAP Sensor -P0107, P0108 (1997-2003 5.2L, 5.9L V8 Dodge Ram Pickup)

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:

1. 1

   Unplug the MAP sensor from its 3-wire connector harness.

2. 2

   Connect the black multimeter's test lead to the battery's negative (-) terminal.

3. 3

   Switch your multimeter to the DC voltage setting.

4. 4

   Turn the ignition to the ON position —but do not start the engine.

5. 5

   Use the red multimeter lead to test the terminal that connects to the wire I've labeled with the number 1 (see image above).
   
   NOTE: Make sure this terminal corresponds to the ORG or VIO/WHT wire on the sensor's 3-wire connector.

6. 6

   You'll get one of two voltage readings:
   
   1.) Between 4.5 and 5 Volts DC —this means the sensor is receiving power.
   
   2.) 0 Volts —indicating no voltage is being delivered to the MAP sensor.

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: TEST 3: Verifying The MAP Sensor Ground Circuit.

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 pickup.

TEST 3: Verifying The MAP Sensor Ground Circuit

If you've reached this point, you now know two things:

1. The MAP sensor is not producing a signal when you applied vacuum to it in TEST 1.
2. That it's getting power, in the form of 5 Volts DC (TEST 2).

The next step (after verifying the MAP signal and power circuit) is to make sure that the MAP sensor on your Dodge Ram pickup has a good path to Ground.

The wire that delivers this Ground to the MAP sensor is the black with light blue stripe (BLK/LT BLU) wire of the sensor's connector.

This is also a pretty easy test, in which you'll use your multimeter once again.

IMPORTANT: Since this circuit is directly connected to the PCM, be very careful and don't short this wire to battery power (12 Volts), or you WILL FRY the PCM.

Alright, this is what you'll need to do:

1. 1

   Unplug the MAP sensor from its 3-wire connector harness.

2. 2

   Connect the red multimeter's test lead to the battery's positive (+) terminal.

3. 3

   Switch your multimeter to the DC voltage setting.

4. 4

   Turn the ignition to the ON position —but do not start the engine.

5. 5

   Use the black multimeter lead to test the terminal that connects to the wire I've labeled with the number 3 (see image above).
   
   NOTE: Make sure this terminal corresponds to the BLK/LT BLU wire on the sensor's 3-wire connector.

6. 6

   You should a voltage reading between 10 to 12 Volts DC.

OK, let's take a look at what your results mean:

CASE 1: The multimeter registered 10 to 12 Volts. This means that the MAP sensor is being supplied with Ground (by the PCM).

It also confirms that the MAP sensor is bad and needs to be replaced if you have:

• Confirmed in TEST 1 that the MAP sensor is not producing the correct values (when you applied vacuum).
• Confirmed in TEST 2 that it's getting power.
• In this test step, you have confirmed that the MAP sensor does have a solid path to Ground.

If you'd like to save a few bucks on the MAP sensor, check out the following section: Where To Buy The MAP Sensor And Save.

CASE 2: The multimeter DID NOT register 10 to 12 Volts. Double check your multimeter connections and repeat the test.

If your multimeter results still do not indicate the presence of Ground, then the reason the MAP sensor is not functioning (producing a signal) is due to this lack of Ground.

MAP Sensor Code Won't Go Away

So you've tested the MAP sensor and according to the test results, it's good. But the check engine light keeps coming back on even after you erased the diagnostic trouble code (DTC) from the computer's (PCM) memory. Well, here are a couple of suggestions that might inspire your next diagnostic move:

1. Major vacuum leak: A major vacuum leak is leaning out the air/fuel mixture that's provoking a rough idle and fooling the PCM into thinking the MAP is at fault.
2. Damaged vacuum elbow: The MAP sensor's rubber elbow (that connects it to the vacuum outlet nipple on the throttle body), has dry rot and/or is broken.
3. Low engine compression: The engine has several cylinders with very low engine compression causing it to idle rough and thus producing low or erratic vacuum. For this I suggest a compression test:
   • How To Test Engine Compression (1989-2003 5.2L, 5.9L V8 Dodge Ram Pickup).
4. Intermittent MAP sensor failure: The MAP sensor is failing intermittently. Which means that it works fine most of the time, but every now and then it doesn't:
   • I have found that the best way to test these intermittent problems is to slightly tap the MAP sensor with the handle of a screw-driver and see if this tapping screws up the voltage readings as I apply vacuum.
5. Damaged MAP sensor connector: The MAP sensor's connector is bad, usually the locking tab is broken and the connector has worked itself loose, causing an intermittent false connection.
6. Failing fuel pump: Your fuel pump is starting to go bad and is not sending enough fuel and/or fuel pressure up to the fuel injectors. I suggest testing the fuel pump with a fuel pressure gauge and see if it's at specification.

More 5.2L, 5.9L V8 Dodge Ram Pickup Test Articles

I've written several more tutorials that may be of interest to you that you can find in this index:

• 5.2L, 5.9L V8 Dodge Ram Pickup Index Of Articles.

Here's a sample of the tutorials you'll find in the index:

• How To Test The Intake Air Temp (IAT) Sensor (1998-2003 5.2L, 5.9L V8 Dodge Ram Pickup).
• How To Test The Fuel Pump (1992-2003 5.2L, 5.9L V8 Dodge Ram Pickup).
• How To Test Engine Compression (1989-2003 5.2L, 5.9L V8 Dodge Ram Pickup).
• Testing The Oxygen Sensors (1996-2003 5.2L, 5.9L V8 Dodge Ram Pickup).