How to Test the MAP Sensor
(Jeep 4.0L)

How to Test  the MAP Sensor (Jeep 2.5L, 4.0L, 5.2L)

The Manifold Absolute Pressure (MAP) Sensor on your 2.5L, 4.0L Jeep Grand Cherokee, or Wrangler, or Cherokee, can be tested with a Multimeter and a Vacuum Pump. You don’t need a Scan Tool! So if a Diagnostic Trouble Code P0108 (OBD II equipped) or a DTC 13, 14 (pre-1995 OBD I equipped) is lighting up the Check Engine Light (CEL) on your Jeep SUV, this is the article for you.

This article will show you how to do a very accurate MAP Sensor Test that’s explained in step-by-step detail. The MAP Test described here in this article can be done in under 15 minutes and covers two different styles of MAP Sensor.

To help you navigate this article a little easier, here are its contents at a quick glance:

  1. MAP SENSOR TEST 1: Checking the MAP Signal.
  2. MAP SENSOR TEST 2: Checking the Power Circuit.
  3. MAP SENSOR TEST 3: Checking the Ground Circuit.
  4. Symptoms of a BAD MAP Sensor.
  5. Related Test Articles.

NOTE: For the MAP sensor test covering the 1997-2003 4.0L equipped Grand Cherokee, Cherokee, and Wrangler... go to this tutorial: How to Test the MAP Sensor (1997-2003 Jeep 4.0L).

MAP SENSOR TEST 1: Checking the MAP Signal

The very first thing that you’ll do, is to test the Signal that the MAP Sensor is generating while applying vacuum with a Vacuum Pump.

If you don’t have a Vacuum Pump, you can run down to your local Auto Parts Store (like AutoZone or O’reilly) and you can rent one from them (and when you get the chance, buy one online).

OK, to get this show on the road, this is what you need to do:

  1. 1

    Disconnect the Vacuum Hose from the MAP Sensor but leave the MAP Sensor connected to its electrical connector.

  2. 2

    Now, connect the Vacuum Pump to the MAP Sensor using a small piece of Vacuum Hose.

  3. 3

    Set your Multimeter’s selector in Volts DC and with the RED Multimeter Test Lead connected to a Wire Piercing Probe, pierce the wire labeled with the number 2 in the image viewer.

    To see what a what wire piercing probe tool looks like, click here: Wire Piercing Probe.

  4. 4

    Ground the BLACK Multimeter Test Lead directly on the Battery Negative Terminal.

  5. 5

    Turn the Key on but don’t start the Engine. By turning the Key to On, the MAP Sensor will get the power (in the form of 5 Volts DC) to be able to do this test.

  6. 6

    Now, as you actuate the Vacuum Pump to apply vacuum to the MAP Sensor, you’ll should see:

    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.

OK, let’s take a look at what your Vacuum Pump Test results mean:

CASE 1: The Vacuum Pump’s Gauge registered the indicated Vacuum readings, this result verifies that the Manifold Absolute Pressure (MAP) Sensor on your Jeep 4.0L Grand Cherokee (or Wrangler or Cherokee) is good and not BAD. You can stop here, since no further testing is required.

CASE 2: The Vacuum Pump’s Gauge DID NOT register the indicated Vacuum readings, This usually means that the MAP Sensor is fried. To be absolutely sure, I suggest confirming that the MAP Sensor has power and ground. If both (power and ground) are present, the MAP is BAD. To test for power, go to MAP TEST 2.

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

“I cook with wine, sometimes I even add it to the food.”
W.C. Fields