The MAP sensor, on the 1999, 2000, and 2001 4.7L Jeep Grand Cherokee, can be tested without a scan tool.
In this tutorial, I'll show you how to test it using a multimeter. This multimeter test will accurately tell you if the MAP sensor is bad or not.
Contents of this tutorial:
Symptoms Of A Bad MAP Sensor
The fuel system on your 4.7L Jeep Grand Cherokee is a ‘speed density’ type. Which, in layman's terms, means that it needs 3 inputs to calculate the amount of fuel to inject for any given amount of air entering the engine. These 3 inputs are engine speed, engine vacuum (manifold pressure), and air intake temperature.
The MAP sensor is the one that provides the engine vacuum (manifold pressure) input to your Grand Cherokee's fuel injection computer. Since it's such a critical input sensor, when the it fails, it causes quite a bit of havoc on engine performance.
The most obvious symptom, of a failed MAP sensor, is the check engine light (CEL) will be shining nice and bright (and a MAP sensor trouble code stored in the PCM's memory). But it's not the only one. You may see one or more of the following symptoms:
- Diagnostic trouble codes (DTCs):
- P0106: Manifold Absolute Pressure Sensor Performance.
- P0107: Manifold Absolute Pressure Sensor (MAP) Circuit Low.
- P0108: Manifold Absolute Pressure Sensor (MAP) Circuit High.
- Doesn't pass the smog check.
- Engine idles rough.
- Engine takes forever to start (extended cranking time).
- Engine doesn't start.
- Black smoke coming out of the tail-pipe as engine runs.
Let's jump into the first test in the next subheading.
TEST 1: Checking The MAP Sensor Signal
In a nutshell, to test the MAP sensor we need to connect a multimeter to its signal wire and apply vacuum to it while we read the signal wire voltage output.
Now, we're not gonna' use the engine's vacuum to test it. We're gonna' manually apply this vacuum with a vacuum pump. Why? Because applying vacuum with a vacuum pump and bypassing the engine's vacuum is the most accurate way of testing the MAP sensor.
By the way, the dark green w/ orange stripe (DK GRN/ORG) wire is the one that transmits the MAP signal to the PCM and is the one we'll tap into with the multimeter.
Don't worry, this is a pretty easy test and in you'll find it all explained in a step-by-step manner below.
OK, these are the test steps:
Remove the MAP sensor from its place on the intake manifold.
Connect your vacuum pump to the MAP sensor's vacuum port using a vacuum hose. Before you proceed to the next step, make sure the MAP sensor is connected to its connector.
With your multimeter in Volts DC mode probe the DK GRN/ORG wire of the MAP sensor connector with the red multimeter probe. The DK GRN/ORG wire is the one that connects to MAP sensor pin #2 in the illustration above.
You'll need to use a tool like a wire piercing probe to access the signal inside the wire. To see what a wire piercing probe looks like, go here: Wire Piercing Probe (at: easyautodiagnostics.com).
Connect the black multimeter test lead directly to the battery negative (-) terminal.
Turn the key ON but don't start the engine. At this point your multimeter should register about 3.8 to 4.0 Volts DC.
Now, pump the vacuum pump to apply vacuum to the MAP sensor. The voltage should drop down to 1.1 Volts.
Repeat this test step several times and each time, you should see the same values on your multimeter.
OK, let's take a look at what your vacuum pump test results mean:
CASE 1: Your multimeter registered the indicated voltages as you applied vacuum. This tells you that the manifold absolute pressure sensor is OK (not defective).
Now, if your vehicle still has the MAP sensor code lighting up the check engine on your instrument cluster, take a look at the section: MAP Code Won't Go Away for more info.
CASE 2: Your multimeter registered voltage, but it did not increase or decrease as you applied vacuum. This confirms that the manifold absolute pressure (MAP) sensor on your 4.7L Dodge is bad. Replacing the MAP sensor will solve the MAP sensor trouble code lighting up the check engine light.
CASE 3: Your multimeter registered 0 Volts. 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 sensor is bad To test for power, go to: TEST 2: Verifying The Manifold Absolute Pressure Sensor Is Getting Power.