Cutlass L4-138 2.3L VIN A FI HP (1990)
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 and spark calculations. 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 to 2.3 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.
3.
Check vacuum hose to sensor for leaking or restriction. Be sure no other vacuum devices are connected to the MAP hose.