[old_master]

The MAP sensor is supplied reference voltage of approximately 5VDC from the ECM on the grey wire. The purple wire is sensor ground from the ECM. The Manifold Absolute Pressure, or MAP sensor, measures the absolute pressure inside the intake manifold. While the engine is at idle, vacuum is high, in other words, a negative pressure. When the engine is at wide open throttle, (WOT) manifold vacuum is near zero, or, atmospheric pressure. The MAP sensor measures these values and sends the data to the ECM through the light green wire. Here's where the problem is. You measured voltage on the light green wire near the MAP sensor, (connected and ignition in RUN position) and showed zero volts. DTC 34 states low voltage/high vacuum. In fact, the DTC is correct, there is no voltage signal being received from the MAP sensor at the ECM.

With the sensor unplugged you measured 1.4 ohms to ground on the llight green wire. We need to find out if the wire is shorted to ground somewhere in the harness, or if it's shorted to the purple wire, which is also ground.

Next step:
Ignition off, negative battery cable disconnected, unplug MAP sensor, unplug ECM: In the ECM connector "C", pin #11 is the light green wire. Check resistance from the ECM harness connector to the MAP sensor light green wire terminal. Have an assistant wiggle the harness while checking resistance. Must remain less than 5 ohms.

Then check resistance from the purple wire to the light green wire at the MAP sensor harness connector. Must indicate open or "infinite" resistance.

Next, check resistance from ECM connector "C" pin #11, (light green wire) to ECM connector "D" pin #2, purple wire. Must indicate open or "infinite" resistance.

Then check resistance of purple wire to ground at ECM connector and at MAP connector.