Guide to the MAP Sensor for Diesel Trucks

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MAP stands for Manifold Absolute Pressure. The MAP sensor’s function is to measure the pressure of the engine’s intake manifold and send that information to the ECM or Engine Control Module.

The ECM uses information from the MAP sensor to adjust the air-fuel ratio of your engine and the ignition timing. As you might suspect, a functioning MAP sensor is crucial for maintaining good performance, emissions, and fuel economy.

If you have a faulty MAP sensor, you may experience issues like sluggish throttle response, a rough idle, poor fuel economy, or a check engine light.

Is the MAP sensor easy to clean? Can you keep driving your truck if it’s bad? ProSource is here to answer these questions and more. ProSource Diesel takes a look at the MAP sensor for diesel trucks, how to test it, how to clean it, and how to identify symptoms of a faulty one.

What is a MAP Sensor?

A MAP sensor is one of several sensors found in fuel-injected engines. It’s used by the ECM to calculate air-fuel ratio by monitoring the intake manifold pressure. In many cases, an MAF or Mass Air Flow sensor is used in place of a MAP sensor.

However, turbocharged engines, which include the diesel engines in Ram, Ford, and GM trucks, use both a MAP and an MAF sensor. The ECM requires information from a properly functioning MAP sensor to optimize performance. A bad air-fuel ratio will cause performance and efficiency issues.

What Does a MAP Sensor Do?

The MAP sensor has two roles. It initially acts like a barometric pressure sensor when the key is turned on. There’s no engine vacuum before the engine is started, but the MAP sensor still sends a barometric pressure reading to the ECM, which helps determine air density.

When you start the engine, the pressure in the intake manifold goes down, which creates a vacuum that the MAP sensor reads. When you step on the accelerator pedal, the intake manifold pressure rises, reducing the vacuum.

The pressure difference moves the chip up into the sealed chamber, causing a voltage resistance and sending that information to the ECM. When there’s no pressure on the accelerator pedal, the intake manifold pressure goes down and the chip goes back to an idle state.

Where Is the MAP Sensor Located?

In general, the MAP sensor is located somewhere on the intake manifold near the throttle body. The exact location depends on the engine.

For example, the MAP sensor on the 2008-2010 Powerstroke engine is located on the intake manifold, either next to or on the throttle body on the passenger side of the engine towards the front of the engine.

The 2020-2024 Duramax L5P has the MAP sensor on top of the intake manifold.

For Cummins engines, the MAP sensor is usually located on the back end of the intake manifold plate.

What Are the Symptoms of a Faulty MAP Sensor?

Like many of the sensors in your engine, the MAP sensor is vulnerable to contamination. Vibration and heat from the engine can loosen, break, or melt its connections. In these scenarios, the MAP sensor will likely need to be replaced.

Ultimately, a bad or failing MAP sensor will affect the air-fuel ratio of the engine. Some bad MAP sensor symptoms include the following:

Check engine light
Misfire
Rough idle
Poor fuel economy
Sluggish acceleration
Stalling
Hesitation
Backfiring through the intake
Overheating

There are also several OBD-II codes associated with the MAP sensor. These include:

P0068: MAP/MAF – Throttle Position Correlation
P0069: Manifold Absolute Pressure – Barometric Pressure Correlation
P0105: MAP Circuit Malfunction
P0106: MAP/Barometric Pressure Circuit Range/Performance Problem
P0107: Manifold Absolute Pressure/Barometric Pressure Circuit Low Input
P0108: MAP Pressure Circuit High Input
P0109: MAP / Baro Pressure Circuit Intermittent
P1106: MAP/BARO Pressure Circuit Range/Performance Problem
P1107: Barometric Pressure Sensor Circuit Low Voltage

It’s possible for other parts or sensors to throw the above codes, so if your engine throws one of these codes and has the symptoms listed above, you should still test the MAP sensor to confirm that it’s faulty.

How To Test a MAP Sensor

Before you test the MAP sensor, check the physical appearance of the sensor and the area around it.

Inspect the connector and wiring for signs of melting or cracking. Ensure that there are no loose connections.

Next, disconnect the MAP sensor and look at the pins. There shouldn’t be any bent pins or signs of corrosion.

If there’s a hose connecting the sensor to the manifold, then check it for any signs of damage.

If all of that checks out, then you can proceed to test the MAP sensor with a digital multimeter set on 20V and a vacuum pump. Multimeters and vacuum pumps like the ones below can be found on Amazon or locally at Harbor Freight, Home Depot and similar stores.

Step 1 – Keep the engine off and connect the multimeter ground to the negative battery terminal. Check the voltage of the battery and ensure it’s around 12.6 volts.

Step 2 – Check your service manual to ascertain the signal ground and 5V reference. Back-probe the wires.

Step 3 – Turn the key on, but don’t start the engine. The multimeter should display a voltage reading of 4.5-5 volts for the 5V reference. It should show 0 volts for the ground wire and 2.0-3.0 volts for turbo engines. Confirm the specs of your exact engine with your owner’s manual.

Step 4 – With the signal wire back-probed, start your engine and check the multimeter. It should show between 2.0-2.5 on a turbocharged engine.

Step 5 – Turn the engine off, but keep the key switched on.

Step 6 – Disconnect the MAP sensor from the intake and connect a hand vacuum pump. Note the voltage from the signal wire.

Step 7 – Increase the vacuum on the sensor with the pump and check to see if the voltage drops as the vacuum increases.

If the changes in voltage are erratic or show large differences in either test, then your MAP sensor is faulty and needs to be replaced. The exact steps to replace a MAP sensor vary by vehicle, so it’s important to consult your service manual.

How To Clean a MAP Sensor

It’s possible that a MAP sensor can behave erratically if it’s dirty. You can clean a MAP sensor with a spray designed to do this. Don’t physically touch the actual sensor and don’t use compressed air. There are conflicting opinions on whether you can use MAF cleaner on the MAP sensor. In fact, one person said that cleaning their MAP with MAF cleaner damaged it.

You can also check connected components and clean them as well. MAP sensors are vulnerable to contamination and can become clogged or dirty. However, it’s important to use a cleaner meant for this purpose and not something like brake cleaner.

Due to the low cost of a new MAP sensor and the ease of removing and putting in a replacement, we recommend just replacing it about every 60k miles.

How To Reset a MAP Sensor

In general, your vehicle’s computer should reset all related codes when you resume driving with the new MAP sensor. If this doesn’t happen after replacing it, you may need to consult your service manual to check if there’s a specific process to follow.

Technically, you can keep driving your truck if your MAP sensor is bad, but it’s likely to cause some performance issues and can eventually cause engine damage, so it’s best to replace a bad sensor as soon as possible.

You can count on ProSource Diesel for replacement MAP sensors on Cummins, Powerstroke, and Duramax engines, as well as various accessories to help you install them.

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