MAP SENSOR TEST 2: Checking The Power Circuit

How To Test The MAP Sensor With A Multimeter (Jeep 2.5L, 4.0L, 5.2L)

So far, in MAP TEST 1, you have verified that the MAP sensor on your Jeep SUV (Wrangle, Cherokee, Grand Cherokee) is not creating a signal or the signal is erratic.

An so, in this MAP sensor test step, you're gonna' verify that the MAP sensor is getting power, since without power it won't work. This power come in the form of 5 Volts and the PCM (Powertrain Control Module = Fuel Injection Computer) is the one that provides this juice.

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

    Place your multimeter in Volts DC mode.

  2. 2

    Disconnect the MAP sensor from its electrical connector.

  3. 3

    With the red multimeter test lead, gently probe the female terminal labeled with the number 1 in the photo above.

  4. 4

    Connect the black multimeter test lead on the battery's negative (-) post.

  5. 5

    Turn the key to the ON position but don't crank or start the engine.

  6. 6

    Your multimeter should register 4.5 to 5 Volts DC.

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. 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: MAP SENSOR TEST 3: Checking The Ground Circuit.

CASE 2: The multimeter DID NOT register 5 Volts. This results lets you know that the reason the MAP sensor is not bad, since without these 5 Volts DC, the MAP sensor can not function.

MAP SENSOR TEST 3: Checking The Ground Circuit

How To Test The MAP Sensor With A Multimeter (Jeep 2.5L, 4.0L, 5.2L)

The next step (after verifying the MAP signal and power circuit) is to make sure that the MAP sensor on your Jeep SUV has a good path to Ground. So, in this test step, you're gonna' verify that the MAP sensor is getting Ground using your multimeter once again.

IMPORTANT: This wire (circuit) connects directly 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

    Place your multimeter in Volts DC mode.

  2. 2

    Disconnect the MAP sensor from its electrical connector.

  3. 3

    With the black multimeter test lead, gently probe the female terminal labeled with the number 3 in the photo above.

  4. 4

    Connect the red multimeter test lead on the battery's positive (+) post.

  5. 5

    Turn the key to the ON position but don't crank or start the engine.

  6. 6

    Your multimeter should register 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 is the correct and expected test result.

You can conclude that the MAP sensor, on your Jeep Grand Cherokee (Wrangler, Cherokee), is fried and needs to be replaced if you have:

  • Confirmed that the MAP sensor's signal voltage does NOT decrease/increase as you apply/release vacuum to the sensor (TEST 1).
  • Confirmed that the MAP sensor is getting 5 Volts DC (TEST 2).
  • In this section, you have confirmed that the MAP sensor is getting Ground.

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 12 Volts, then the MAP is not fried and not the cause of the MAP diagnostic trouble code (DTC) issue.

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.

More 4.0L Jeep Diagnostics Tutorials

I've written several more tutorials that may be of interest to you. These are specific Jeep 4.0L Cherokee (or Grand Cherokee, Wrangler) at:

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

Thank You For Your Donation

If this info saved the day, buy me a beer!

If This Info Saved the Day, Buy Me a Beer!

Jeep Vehicles:

  • Cherokee 2.5L, 4.0L
    • 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995
  • Comanche 2.5L, 4.0L
    • 1987, 1988, 1989, 1990, 1991, 1992
  • Grand Cherokee 4.0L
    • 1993, 1994, 1995

Jeep Vehicles:

  • Wagoneer 2.5L, 4.0L
    • 1987, 1988, 1989, 1990
  • Wrangler 2.5L, 4.0L
    • 1986, 1987, 1989, 1990, 1991, 1992, 1993, 1994, 1995