MAP Sensor Quick-Fix

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MAP Sensor Quick-Fix

The MAP sensor, is a 3 wire sensor, that measures intake manifold vacuum. The ECM,uses this value,to calculate fuel injection open time.

To test the MAP sensor, and circuit, do the following, with MAP sensor disconnected.

1) First check the ECM circuit, by checking for 5 volts, at one of the 3 MAP sensor wires.
2) Check sensor ground. Check voltage between battery positive, and one of the MAP sensor wires, either or is fine.
3) Reconnect MAP sensor, then backprobe center wire, should have under 1 volt. That's it for circuit check.

Then, while probing on center signal wire, start engine. If engine won't start, due to no injection, then it's not the MAP sensor. MAP causes stumble and rough idle, not no start. If no start, use the No Start Trubleshooter Software for extended help.

Finally, with MAP sensor, and voltmeter connected, remove MAP sensor, plug a hose to it, and suck on it. You should see voltage fluctuating. If so, then engine no start is due to another reason. If engine starts, then use the waveform database, to determine proper idle running value, and fuel trims at plus or minus 10%. That's all for the MAP sensor quick fix.