The manifold absolute pressure (MAP) sensor is an important component of your vehicle's engine management system. It's one of the many input sensors the fuel injection computer relies upon to keep the engine running smoothly.
In this article, you'll find answers to some of the most commonly asked questions about the MAP sensor.
Contents of this tutorial:
- What Does A MAP Sensor Do?
- What Happens When A MAP Sensor Goes Bad?
- What Problems Can A MAP Sensor Cause?
- How Can You Tell If A MAP Sensor Is Bad?
- How Can I Find Out If The MAP Sensor Is Bad?
- Can I Drive My Vehicle With A Bad MAP Sensor?
- Where To Buy The MAP Sensor And Save.
- More 3.1L V6 Chevrolet, Pontiac Tutorials.
This tutorial applies to the following vehicles:
- 3.1L V6 Chevrolet Beretta: 1994, 1995, 1996.
- 3.1L V6 Chevrolet Corsica: 1994, 1995, 1996.
- 3.1L V6 Chevrolet Lumina: 1995, 1996, 1997, 1998, 1999, 2000, 2001.
- 3.1L V6 Chevrolet Malibu: 1997, 1998, 1999, 2000, 2001, 2002, 2003.
- 3.1L V6 Chevrolet Monte Carlo: 1995, 1996, 1997, 1998, 1999.
- 3.1L V6 Pontiac Grand Am: 1994, 1995, 1996, 1997, 1998.
- 3.1L V6 Pontiac Grand Prix: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003.
What Does A MAP Sensor Do?
In a nutshell, the MAP sensor is responsible for measuring the vacuum pressure inside the intake manifold.
If your vehicle does not come equipped with a MAF sensor, the MAP sensor is part of a triad of input sensors that the fuel injection computer uses to calculate the amount of air entering the engine as it runs.
This triad of sensors is the MAP sensor, the intake air temperature (IAT) sensor, and the crankshaft position (CKP) sensor.
If your vehicle comes equipped with a MAF sensor, then the fuel injection computer uses the MAP sensor to:
- Take a barometric pressure reading right before you start the engine.
- To receive engine load input once the engine starts.
What Happens When A MAP Sensor Goes Bad?
When the MAP sensor fails, it simply stops measuring the intake manifold's vacuum.
Without this intake manifold vacuum measurement, the fuel injection computer cannot calculate the engine's load. This in turn will cause drivability, emissions, and engine performance problems.
I'll go into more detail about the symptoms you'll see when the MAP sensor fails in the next section.
What Problems Can A MAP Sensor Cause?
The fuel injection computer constantly monitors the MAP sensor's output. When it fails, the computer will set one of the following trouble codes and illuminate the check engine light:
- On OBD II equipped vehicles (1995 or newer), you'll see:
- P0106: MAP Sensor System Performance.
- P0107: MAP Sensor Circuit Low Voltage.
- P0108: MAP Sensor Circuit High Voltage.
- On OBD I equipped vehicles (1994 or older), you'll see:
- 33: MAP Sensor Signal Voltage High.
- 34: MAP Sensor Signal Voltage Low.
You're also going to see one or more of the following symptoms:
- Bad gas mileage.
- Lack of power.
- Black smoke coming out of the tailpipe.
- Engine suffers a very rough idle.
- The engine may start and immediately stall.
- The engine has to be cranked longer than usual for it to start (this is called extended cranking).
- A heavier than normal exhaust smell when the engine is running.
- Won't pass the emissions test.
How Can You Tell If A MAP Sensor Is Bad?
Simply put, the best way to find out if the MAP sensor has failed is to test it.
In the next section, I'll explain the basic MAP sensor testing procedure.
How Can I Find Out If The MAP Sensor Is Bad?
A MAP sensor can easily be diagnosed as bad by performing a simple multimeter test on it.
Here's the basic MAP sensor test procedure:
- Check for MAP sensor trouble codes with a code reader or scan tool.
- Make sure that the MAP sensor is receiving 5 Volts DC.
- Make sure that the MAP sensor is receiving Ground.
- Make sure that the sensor's MAP voltage signal increases/decreases as vacuum is applied/released to it.
If the MAP voltage signal does not increase/decrease as you apply/release vacuum to the MAP sensor, then you can conclude that your vehicle's MAP sensor is bad and needs replacement.
I've written a tutorial that'll help you test the MAP sensor using a vacuum pump and a multimeter. You can find it here:
Can I Drive My Vehicle With A Bad MAP Sensor?
Depending on the severity of the symptoms the faulty MAP sensor is causing, you probably won't be able to drive the vehicle. But even if you could, you should avoid doing so.
Why? Because when the MAP sensor fails, it's either going to cause the fuel injection computer to inject too much fuel or not enough.
If too much fuel is injected into the engine cylinders, you risk:
- Damage to the catalytic converter.
- Accelerated wear and tear on the piston rings.
- Fuel will seep into the crankcase (across the piston rings). This fuel will eventually start to dilute the engine oil.
If the MAP sensor is causing the fuel injection computer to inject less fuel, then you risk:
- Damage to the cylinder intake and exhaust valves. This is due to the fact that the engine is running on a lean air fuel mixture that will cause the cylinder head valves to run hotter than usual.
Any electronic fuel injection system problem should be diagnosed and resolved as soon as possible.
Where To Buy The MAP Sensor And Save
The following MAP sensors are all from known automotive brands (no knockoffs!). They fit the 3.1L V6 Chevrolet and Pontiac vehicles covered by this tutorial.
More 3.1L V6 Chevrolet, Pontiac Tutorials
You can find a complete list of 3.1L V6 Chevrolet (Pontiac) tutorials in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test A Blown Head Gasket (3.1L V6 Chevrolet, Pontiac).
- How To Test The Engine Compression (3.1L V6 Chevrolet, Pontiac).
- How To Test The Fuel Pump (1995-1999 3.1L V6 Chevrolet Lumina, Monte Carlo).
- How To Test The MAP Sensor (3.1L V6 Chevrolet, Pontiac).
If this info really saved the day, buy me a beer!