Chart C-1D Manifold Absolute Pressure (MAP) Output Check

Manifold Absolute Pressure (MAP) Output Check:

Wiring Diagram for Chart C-1D - Manifold Absolute Pressure (MAP) Output Check:

CIRCUIT DESCRIPTION
The Manifold Absolute Pressure (MAP) sensor measures manifold pressure (vacuum) and sends that signal to the Electronic Control Module (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 63 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.