How To Test a Chevy Astro MAP Sensor

How To Test a Chevy Astro MAP Sensor


When your Chevy Astro MAP sensor is beginning to go bad, you can use this handy How To Guide to test it. The MAP (Manifold Absolute Pressure) sensor is responsible for reading the atmospheric pressure of the air coming into your engine. Today I’ll be showing you how to test this pressure sensor in a 2001 Chevrolet Astro van.

The engine powering our test vehicle is a GMC 4.3 L V6, and the MAP sensor is mounted externally.


This sensor is a standard 3 pin MAP style unit with 3 wires; power, ground and signal. Some of the more common OBDII trouble codes that can spring up from a failing MAP sensor are P0106,  P0107 or P0108.

If you own a Astro that’s built before 1995, it’s a OBDI vehicle. The trouble code for the OBDI Astro is a Code 33 Manifold Absolute Pressure Sensor Circuit High Signal or Code 34 Circuit Low Signal.


How To Test Chevy Astro MAP Sensor

The aftermarket part number for your Chevy Astro MAP sensor is AS59. This part is mounted externally to your intake manifold, and is connected to a three pin weatherproof connector.

To begin testing your MAP sensor in your Chevy, you will need a multimeter. If you are not certain what a multimeter is, check out our handy guide on how to use one here. Using this tool you will be testing your MAP sensor to see if it’s working correctly.

Testing the Chevy Astro MAP Sensor for Power

To test your sensor use the three pins shown in the Chevy Astro MAP sensor wiring diagram below. Make sure to find your MAP sensor and orientate the pins according to the diagram from left to right, facing towards the MAP connector.

Insert your Astro key into the ignition and turn to the “ON” position. This will send power to all of your engine sensors, but do not turn the engine on. Unplug your MAP sensor connector, and test the PIN A for a 5 volt signal.

Do this by placing the black lead on your negative battery terminal, and gently probing PIN A with the red lead. Do not force or push the lead into the wire connector, as you may damage the connector itself.



If you see that power at this pin, you can test the MAP sensor for a low reference ground signal. PIN C is the terminal you will be testing with your multimeter to see if there’s a ground signal present.

Once you have determined that your Chevy Astro MAP sensor has power and ground, the next thing to do is test the signal wire.

Testing the Chevy Astro MAP Sensor Signal

Just as before you will be turning your ignition to the “ON” position, but do not start the engine. Reconnect your MAP sensor, and get a paper clip to properly backpin the connector.

Because your Chevy Astro MAP sensor must be connected to test the signal wire, you will need to push in the connector. Unfold the paper clip and insert it into the back of PIN B to make a positive connection with the metal connector. Remember you are doing this with the Chevy Astro MAP sensor plugged in.

If your engine is not turned on and no vacuum applied to the MAP sensor, you should see 4.7 volts at this pin. As vacuum increases to the inlet of the MAP sensor, the voltage will decrease.

You can test the operation using a Mighty vac or a similar hand held pumping device. By using the hand pump to increase vacuum, you are effectively replicating the rush of incoming air to your Astro engine.

Using the pump you can begin test the the MAP sensor operation by increasing vacuum to the intake manifold. This can be done through the brake assist hose or any number of the vacuum lines to the engine.

Test the unit by slowing introducing vacuum into your intake manifold. At 20 in. Hg you should see 1.1 Volts DC at PIN B. The voltage should be gradual and should not have any spikes or missing sections of voltage.

You now know how to test your Chevy Astro MAP sensor, and if you see any problems with the voltage signal replace the unit. Have any questions or comments regarding our guide? Leave us a comment below and let us know!