I'm gonna' show you the absolutely best way (and probably one of the most accurate ways) of testing the Manifold Absolute Pressure (MAP) sensor on your 3.3L equipped Chrysler/Dodge mini-van.
Before we get started, let me tell you that this tutorial will show you how to do a MAP sensor bench test... so you'll need a vacuum pump, that you can rent at your local auto parts store (AutoZone, O'Reilly) and can be accomplished in a few minutes. If you don't have access to a vacuum pump... no big deal, you can just just the good ole lungs (more about this in the tests).
Now, in case you're wondering, “Why a bench test?”... this is due to the fact that so many different conditions can trick the fuel injection computer (PCM = Powertrain Control Module) into thinking the MAP sensor is bad when it isn't. So, the best way to find out if the MAP sensor is truly fried or not is by testing it off of the engine.
To help you navigate this article a little easier, here are its contents at a quick glance:
- Symptoms of a BAD MAP Sensor.
- How MAP Sensor Works.
- TEST 1: Verifying the MAP Signal.
- TEST 2: Verifying the MAP Sensor Has Power.
- TEST 3: Verifying the MAP Sensor Ground Circuit.
- MAP Sensor Code Won't Go Away.
Symptoms of a BAD MAP Sensor
When the Manifold Absolute Pressure (MAP) sensor fails, the Check Engine Light will turn on and you'll see one of the following diagnostic trouble codes:
- P0106: MAP System Performance.
- P0107: MAP Sensor Circuit Low Voltage.
- P0108: MAP Sensor Circuit High Voltage.
Besides the diagnostic trouble codes, your Chrysler/Dodge 3.3L mini-van is not gonna' run right. You'll experience one or several of the following symptoms:
- Rough idle.
- Black smoke coming out of the tail-pipe.
- Engine Stalls under load.
- Engine dies as soon as it starts.
- Lack of power when you accelerate the vehicle down the road.
MAP sensors go BAD all of the time... but sometimes some other condition (affecting engine performance) fools the PCM (Powertrain Control Module = Fuel Injection Computer) into thinking that the MAP sensor is has failed.
To be absolutely sure the MAP sensor is BAD or not (without replacing to find out), you need to bench test it... and the MAP sensor test that I'm gonna' show you is a MAP sensor bench test.
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 in your 3.3L equipped Chrysler mini-van is a ‘speed density’ type... which, among other things, means it doesn't use a mass air flow (MAF) sensor to measure the amount of air the engine is breathing.
To be a bit more specific, the PCM uses the MAP sensor to measure the amount of vacuum inside the engine and the crank sensor to know the engine's RPMs to calculate the amount of air entering the engine.
- With both the MAP sensor signal info and crank sensor signal info, the PCM now calculates the approximate amount of air entering the engine and:
- Adjusts fuel injection pulse width and...
- Ignition Timing.
This is what happens when you turn the key and start the engine:
- The PCM feeds 5 Volts to the MAP sensor thru' the wire labeled with the number 3.
- Ground is provided, by the PCM too, thru' the wire labeled with the number 2.
- Once the MAP sensor gets power and ground, it now starts to measure the amount of vacuum the engine is producing and shoots the info to the PCM thru' the wire labeled with the number 1.
The MAP sensor plays a role in the performance and efficient operation of the engine in your 3.3L equipped Chrysler or Dodge mini-van, so, let's turn the page and get testing....