Beretta V6-173 2.8L (1989)
Chart C-1D Wiring Diagram
CIRCUIT DESCRIPTION:
The manifold absolute pressure sensor (MAP) measures manifold pressure (vacuum) and sends that signal to the ECM. The MAP sensor is mainly used
for fuel calculation, when the ECM is running in the throttle body backup mode. The MAP sensor is also used to determine the barometric pressure and
to help calculate fuel delivery.
TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.
1.
Checks MAP sensor output voltage to the ECM. This voltage, without engine running, represents a barometer reading to the ECM.
2.
Applying 34 kPa (10 inches Hg) vacuum to the MAP sensor should cause the voltage to be 1.2 volts less than the voltage at Step 1. Upon applying
vacuum to the sensor, the change in voltage should be instantaneous. A slow voltage change indicates a faulty sensor. The engine must be running
in this step or the "Scanner" will not indicate a change in voltage. It is normal for the "SERVICE ENGINE SOON" light to come "ON" and for the
system to set a Code 33 during this step. Make sure the code is cleared when this test is completed.
3.
Check vacuum hose to sensor for leaking or restriction, Be sure no other vacuum devices are connected to the MAP hose.
