The manifold absolute pressure (MAP) sensor can be accurately tested with a multimeter and a vacuum pump and in this article, I'll show you how.
When the MAP sensor goes bad, you'll usually see one of the following diagnostic trouble codes stored in your Dodge's computer's memory: P0106, P0107, or P0108. If this is the case, this is the article for you.
Contents of this tutorial:
- Symptoms Of A Bad MAP Sensor.
- How The MAP Sensor Works.
- Where To Buy The MAP Sensor And Save.
- TEST 1: Verifying The MAP Signal.
- TEST 2: Making Sure That The MAP Sensor Is Getting Power.
- TEST 3: Verifying The MAP Sensor Ground Circuit.
- MAP Sensor Code Won't Go Away.
- More 5.2L, 5.9L V8 Dodge Ram Pickup Test Articles.
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAP (Dodge 3.9L, 5.2L, 5.9L) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- Dodge Ram 1500 Pickup 5.2L V8: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001.
- Dodge Ram 2500 Pickup 5.2L V8: 1994, 1995, 1996, 1997, 1998.
- Dodge Ram 1500 Pickup 5.9L V8: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003.
- Dodge Ram 2500 Pickup 5.9L V8: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002.
- Dodge Ram 3500 Pickup 5.9L V8: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003.
3.9L V6 Dodge Ram Van MAP Sensor Tests:
The following wiring diagram article may come in handy:
Symptoms Of A Bad MAP Sensor
When the manifold absolute pressure (MAP) sensor fails, the check engine light (CEL) will turn on and you'll see one of the following diagnostic trouble codes:
- P0107: MAP Sensor Voltage Too Low.
- P0108: MAP Sensor Voltage Too High.
Besides the diagnostic trouble codes, your Dodge Ram pickup will experience one or several of the following symptoms:
- Rough idle: When your pickup is stopped in Drive —like at a red light— the engine may run unevenly or feel like it's shaking.
- Black exhaust smoke: Black smoke coming from the tailpipe, especially during acceleration.
- Unexpected stalling: The engine might suddenly shut down with no warning, whether you're easing off the gas or just beginning to accelerate.
- Stalls right after start-up: The engine starts up normally but then immediately cuts off within seconds of running.
- Reduced engine power: You'll notice poor acceleration or a sluggish response when trying to increase speed, feels like the engine is underpowered.
- Limp-in mode activation: To safeguard the engine from further harm, the fuel injection computer engages limp-in mode —drastically cutting power output and hurting gas mileage.
It's rare for the MAP sensor to go bad but it doesn't mean they don't. What usually happens is that some other condition (affecting engine performance) fools the PCM (Powertrain Control Module = fuel injection computer) into thinking that the MAP sensor is bad. So it's always a good idea to test it before replacing it.
In my experience, the absolute best way to test the MAP sensor is to bench test it (and this is how I'm gonna' show you how to tested in this article). By bench testing it, you can eliminate the other possibles that may be fooling the MAP sensor into sending a bad signal to the PCM.
If after doing the MAP sensor test and the MAP sensor is good, then take a look at the section: MAP Sensor Code Won't Go Away.
How The MAP Sensor Works
The fuel system on your 3.9L, 5.2L, 5.9L is a ‘Speed Density’ type. Which in lay man's terms means that it doesn't use a mass air flow (MAF) sensor to determine the amount of air that enters the engine.
In a ‘Speed Density’ fuel system, the PCM relies heavily on MAP sensor and engine RPM input to find out how much air the engine is breathing. Once it has calculated the amount of incoming air, it can then calculate the correct amount of fuel to inject (among several things).
OK, in a nutshell, cause I know you're probably itching to get testing, when you turn the key and crank the engine:
- The PCM supplies voltage to the MAP sensor. This power is the in form of 5 Volts.
- This voltage is provided thru' the wire labeled with the number 1.
- The PCM also provides Ground to the MAP sensor
- This Ground is provided thru' the wire labeled with the number 3.
- Once the MAP sensor gets power and Ground, it now starts to measure the amount of vacuum the engine is producing.
- With both the MAP sensor signal info and crank sensor signal info, the PCM now calculates the approximate amount of air entering the engine. It also:
- Adjusts fuel injection pulse width
- Adjusts the ignition timing.
Since the MAP sensor plays such a critical role in the performance and efficient operation of the engine in your pickup (van, SUV), when it goes bad, your vehicle is gonna' be in a world of hurt.
Where To Buy The MAP Sensor And Save
You can buy the MAP sensor for your Dodge pickup (van, SUV) in just about any auto parts store but you'll spend a whole lot more because they mark it up quite a bit.
My suggestion is to buy it online or at least comparison shop to get an idea of how much it costs and how much you can save.
The following links:
Not sure if the above MAP sensor fits your particular Dodge or Jeep? Don't worry, once you get to the site, they'll make sure it fits by asking you the particulars of your vehicle. If it doesn't fit, they'll find you the right one.
TEST 1: Verifying The MAP Signal
The very first thing we'll do is remove the MAP sensor from the throttle body to bench test it.
Although you're gonna' remove the MAP sensor, you'll leave it connected to its electrical connector and then apply vacuum to it. This will verify whether the MAP sensor on your Dodge pickup is fried or not.
The instructions call for a vacuum pump. If you don't have one and you live here in the States, you can run down to your local AutoZone or O'Reilly Auto Parts and rent one for free.
If you can't get your hands on a vacuum pump and you're itching to get started, you can use the good ole' lungs and mouth.
NOTE: You can use an analog or a digital multimeter for this test. If you don't have a multimeter or need to upgrade yours, check out my recommendation here: Buying A Digital Multimeter For Automotive Diagnostic Testing (at: easyautodiagnostics.com).
OK, this is what you need to do:
- 1
Remove the MAP sensor from the intake manifold.
- 2
Connect your vacuum pump to the MAP sensor's vacuum inlet nipple.
IMPORTANT: Remember, the MAP sensor has to remain connected to its connector (this so that the PCM can power it up with voltage and Ground). - 3
Connect the black lead of your multimeter to the battery's negative (-) post.
- 4
Place your multimeter in Volts DC mode.
- 5
Probe the wire labeled with number 2 with the red multimeter test lead (see the image above).
NOTE: Since the MAP sensor needs to remain connected to its harness connector, you'll need to either back-probe the connector or use a wire piercing probe to get to the signal inside the wire (to see what a wire piercing probe looks like: Wire Piercing Probe Tool). - 6
When all is ready, turn the key ON but don't start the engine.
- 7
With the ignition ON and no vacuum applied, your multimeter should read 4.5 to 4.7 Volts DC.
- 8
Now, apply vacuum to the MAP sensor with the vacuum pump (or your mouth).
You should see following DC voltages at the following vacuum values if you're using a vacuum pump:
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.
NOTE: Whether you're using a vacuum pump or your mouth (to apply vacuum), the voltage on your multimeter should increase and decrease without any gaps or skips on the multimeter. Repeat test steps 1 thru' 5 several times.
OK, let's take a look at what your vacuum pump test results mean:
CASE 1: The voltage increased and decreased smoothly and without gaps. This confirms that the MAP sensor on your Dodge pick up (or SUV or van) is OK and NOT the cause of the problem.
Now, if the PCM is still lighting up the check engine light with a MAP sensor diagnostic trouble code, take a look at the section: MAP Sensor Code Won't Go Away for more info.
CASE 2: Your multimeter registered some voltage, but not as indicated. This tells you that the MAP sensor is fried and needs to be replaced. Replacing the MAP sensor will solve the MAP code issue (P0106, P0107, P0108)
CASE 3: Your multimeter registered 0 Volts. This could mean several things. So further testing is necessary. The next steps (tests) are to make sure 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: Making Sure That The MAP Sensor Is Getting Power.
