The Malibu MAP Sensor in your 3.1 liter Chevy is designed to read the manifold pressure in your intake. Otherwise known as the manifold absolute pressure sensor, this unit plays a big role in how your engine computer controls your engine. When this MAP sensor goes south, your Malibu will run rough and suffer from a poor idle. If your car shows any of the common Chevy Malibu issues related to a failed MAP sensor, this guide can help you.
Today I’ll be showing you how to test the manifold pressure sensor in a 2003 Malibu with a 3.1 liter engine in it. This test will show you conclusively if your MAP sensor has failed or there’s another cause to your Chevy Malibu problem. The Malibu MAP Sensor in your Chevy is a typical GM three pin sensor, connected by way of a weatherproof adapter.
Many of these problems from a bad MAP sensor can range from annoying to severe. Some of the more common Chevy Malibu issues from a bad MAP sensor include:
- Bad gas mileage
- Sluggish performance
- Engine hesitation
- Check Engine Light ON
Some of the more common trouble codes out there can be identified using a OBDII scan tool. This device will be able to retrieve the alphanumeric check engine code in your Chevy computer. Some of the more common check engine codes are P0107: MAP Sensor Circuit Low Voltage or P0108: MAP Sensor Circuit High Voltage.
This guide to testing your Malibu MAP sensor applies even if you happen to own a OBDI Chevy. If that’s the case the trouble codes you’ll see are 33: MAP Sensor Signal Voltage High or 34: MAP Sensor Signal Voltage Low.
Testing your Chevy Malibu MAP for Power
The first leg of our DIY tutorial is to check your MAP connector for power. This is done by inserting your ignition key and turning the ignition to the “ON” position first. Open your hood and locate the MAP sensor which should have a vacuum line from the intake manifold running to it.
Lift the plastic tab and disconnect your Malibu MAP sensor. This is a three pin unit that has slots running down the connectors to prevent plugging it in the wrong way.
You will be using your digital multimeter to test the wiring connectors. This will let you know if your pressure sensor is getting the power and ground signals it needs to operate.
With your connector removed, put the black lead to the negative battery terminal. Now gently touch the red lead to PIN A. Because the connector is made up of three male leads, do your best to avoid grounding the power wire. With your ignition turned to the “ON” position this wire should read 5 volts of DC power.
Next up we’ll be testing for a ground signal. Remember you are testing on the ENGINE harness side of the sensor as shown above in our Malibu MAP Sensor wiring diagram. The pin you are checking for is at WIRE C on the pressure connector. This wire should be a ground signal.
To determine whether or not this ground signal is any good, reverse your multimeter leads and put the red lead to the positive terminal on your battery. Now put the black lead to PIN C on your Malibu MAP sensor harness. You should read 12 volts of signal, which shows your pressure sensor has what it takes to properly operate.
Testing your Chevy Malibu MAP Signal
If your Chevy Malibu is still hard to start and you’ve got power and ground at your MAP the last part of our DIY tutorial is to check for signal. This wire is PIN B and to test this part of our How To you will need to plug the harness back into the sensor.
This part of our DIY Malibu MAP sensor guide will require you to buy or rent a vacuum pump. These automotive tools can be purchased at your local auto parts store or rented. These devices will allow you to apply gentle vacuum to the inlet of your MAP sensor to see if it’s working the right way.
Disconnect the vacuum inlet to your pressure sensor and run it to your vacuum pump. With your Malibu MAP sensor reconnected, pierce the wire that runs to PIN B with the red lead to read the voltage at this wire.
You will now gently apply vacuum pressure to the inlet. Remember to monitor the voltage at PIN B while you do this. The Malibu MAP sensor signal should read 4.7-4.8 volts with no vacuum applied to the inlet.
Now gently increase the vacuum at this port. At 5 in. Hg the Malibu MAP sensor signal should read around 3.9 Volts. Increase the vacuum to 10 in. Hg and the signal should lower to 3.0 Volts. The next step is to apply 20 in. Hg of vacuum at which point the signal wire should be between 1.2-1.1 Volts.
If your Malibu MAP sensor does not respond correctly, remove it and install your replacement pressure sensor. Use your OBDII scan tool to erase your Malibu check engine light. Have any questions about this DIY guide? Leave us a comment below and let us know!
