What Does The MAP Sensor Do? (1.5L Honda Civic)

The manifold absolute pressure (MAP) sensor is a critical engine management system component of your 1.5L Honda Civic.

This tutorial will answer some of the most commonly asked questions about the MAP sensor.

APPLIES TO: This tutorial applies to the following vehicles:

• 1.5L Honda Civic: 1992, 1993, 1994, 1995.
• 1.5L Honda Civic Del Sol: 1993, 1994, 1995.

What Does A MAP Sensor Do?

The MAP sensor's job is to measure and then report the intake manifold vacuum pressure to the fuel injection computer.

The fuel injection computer then uses this information to calculate engine load and the correct amount of fuel to inject into the cylinders.

Here are some more specifics:

• When intake manifold pressure is high, like when the throttle plate is closed, the MAP sensor produces a low voltage value.
• When vacuum pressure is low, like when you step on the accelerator pedal, and the throttle plate opens, the MAP sensor produces a higher voltage output.

In plain English, as more vacuum is applied to the MAP sensor, its voltage output signal decreases. As less vacuum is applied to the MAP sensor, its voltage signal increases.

What Happens When A MAP Sensor Goes Bad?

When the manifold absolute pressure (MAP) sensor fails, it'll stop measuring and reporting the intake manifold vacuum pressure to the fuel injection computer.

This means that no matter what vacuum pressure is applied to the MAP sensor, its voltage output does not decrease/increase.

Since the MAP sensor is a critical component of the engine management system, this will have engine performance repercussions.

The following section will go into more detail.

What Problems Can A MAP Sensor Cause?

Since the fuel injection computer is constantly monitoring the MAP sensor's voltage output, when it fails, you'll see the check engine light illuminated by a MAP sensor diagnostic trouble code.

• Code 3: MAP Sensor Circuit.

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?

The only way to be 100% sure that the MAP sensor has failed is by testing it.

The cool thing is that testing it isn't difficult and can be done with a multimeter. No expensive diagnostic equipment is needed.

See the next section to find out more.

Can I Test The MAP Sensor?

You can easily test the MAP sensor's voltage signal output with a multimeter.

This is the basic MAP sensor testing 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 decreases/increases as vacuum is applied/released to it.

If the MAP sensor's voltage signal does not decrease/increase as you apply/release vacuum to the MAP sensor, then you can conclude that your vehicle's MAP sensor is bad and needs to be replaced.

The following tutorial will help you to test the MAP sensor using a vacuum pump and a multimeter:

• How To Test The MAP Sensor (1992-1995 1.5L Honda Civic).

Can I Drive My Vehicle With A Bad MAP Sensor?

Your Honda Civic's fuel injection computer will activate its 'limp' mode when the manifold absolute pressure (MAP) sensor fails.

'Limp' mode limits your Honda Civic's engine performance to ensure the MAP sensor fault doesn't cause any engine damage.

Depending on the severity of the symptoms that the 'limp' mode or the faulty MAP sensor is causing, your Honda Civic will not be safe to drive.

Where To Buy The MAP Sensor And Save

The MAP sensor is a component that you'll easily find at your local auto parts store or online. Here are my recommendations (of known automotive brand MAP sensors -no knock-offs).

More 1.5L Honda Civic Tutorials

You can find a complete list of 1.5L Honda Civic tutorials in this index:

• 1.5L Honda Civic Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The PGM-FI Main Relay (1992-1995 1.5L Honda Civic).
• How To Test The Fuel Injectors (1992-1995 1.5L Honda Civic).
• How To Test For A Blown Head Gasket (1.5L Honda Civic).
• How To Test Engine Compression (1992-1995 1.5L Honda Civic).