Fault codes don't point to a sensor although that's usually what it turns out to be. They point to the circuit or system. If you got a code related to the MAP sensor, measure the voltages on it. You should find 0.2 volts on the ground wire, 5.0 volts on the feed wire, and somewhere around 1.5 volts on the signal wire at idle. You'll need to back-probe the connector while it's still plugged into the sensor to get the correct readings.
If the signal voltage is high, such as about 3 volts or higher, look for a vacuum leak. The sensor will interpret low vacuum as the engine is under load. That will cause the Engine Computer to request more fuel.
Also be aware there can be other problems that will not set a fault code. The computer has many strategies for figuring out what's making it unhappy, and that includes comparing various parameters to each other. If the MAP reading is used to compare against other sensor data, and the computer knows something is wrong with the MAP reading, it won't be able to perform some other tests. Most commonly this has to do with the oxygen sensors and misfire detection.
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Wednesday, August 10th, 2011 AT 9:37 AM
