How To Test The Manifold Absolute Pressure (MAP) Sensor (GM 2.2L)

MAP Sensor Code Won't Go Away

If you have tested the MAP sensor and it's good or you have replaced it already and yet the fuel injection computer keeps lighting up the check engine light with a MAP sensor code, there's a good chance that you have mechanical problem with your car or pick-up's engine.

Here are a couple of suggestions that might inspire your next diagnostic move:

1. The most common problem I've seen that causes a MAP sensor code (when the MAP is good) is a worn out engine. To be more specific, the engine has several cylinders with very low engine compression causing it to idle rough and thus producing low or erratic vacuum. You should do a compression test:
   • How To Do An Engine Compression Test (GM 2.0L, 2.2L, 2.5L).
2. The MAP sensor's O-rings, the ones located on the vacuum inlet nipple are missing or are too old and they're not sealing properly. Visually check the O-rings and replace if necessary (NOTE: this applies to the MAP sensors that are bolted directly onto the intake manifold and don't use a vacuum hose).
3. The MAP sensor's vacuum hose has dry-rot and is leaking vacuum.
4. The MAP sensor is failing intermittently. Which means that it works fine most of the time, but every now and then it doesn't:
   • I have found that the best way to test these intermittent problems is to slightly tap the MAP sensor with the handle of a screw-driver and see if this tapping screws up the voltage readings as I apply vacuum.
5. The MAP sensor's connector is bad, usually the locking tab is broken and the connector has worked itself loose, causing an intermittent false connection.
6. Your fuel pump is starting to go bad and is not sending enough fuel and/or fuel pressure up to the fuel injectors. I suggest a fuel pump test.

Every now and then, I have worked on a MAP sensor problem that was caused by a bad fuel injection computer. Although this is rare, it does happen.

What I have done, to be sure that a bad fuel injection computer is behind the MAP sensor code or problem was (is) to:

1. Bench test the MAP sensor as described in this tutorial.
2. That there are no vacuum leaks from any of the vacuum hose or the intake manifold gasket(s).
3. Make sure that the engine has good compression on all 4 cylinders.
4. Make sure that the fuel pump is good (as tested with a fuel pressure gauge).
5. Make sure that the 3 wires that connect the MAP sensor to the fuel injection computer have continuity between the MAP connector and the computer's connector.

Once I have confirmed these 5 things (above), I can confidently conclude that the fuel injection computer is bad and replacing it will solve the problem.

Where To Buy The MAP Sensor And Save

If the MAP sensor tests bad and need to replace it, the best place to buy it and save a few bucks is is online.

The following links will help you comparison shop for the original AC Delco (and after-market) MAP sensor:

Not sure if the MAP sensor fits your particular vehicle? Don't worry, once you get to the site they'll make sure it fits by asking you the specifics of your particular GM vehicle. If it doesn't fit, they'll find you the right MAP sensor.

Related Test Articles

I've written several more tutorials that may be of interest to you that you can find at: GM 2.2L Index of Articles.

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

1. How To Test The A/C-Heater Blower Motor (GM 2.2L).
2. How To Do An Engine Compression Test (GM 2.0L, 2.2L, 2.5L).
3. How To Diagnose Misfire Codes (GM 2.2L).
4. Troubleshooting A Blown Head Gasket (GM 2.0L, 2.2L, 2.5L).
5. How To Test The GM 2.2L Ignition Coil Pack (at: easyautodiagnostics.com).