Component Diagnostic Charts - Port Fuel Injection

Chart C-1D:

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. With the ignition "ON," and the engine stopped, the manifold pressure sensor is equal to atmospheric pressure and the signal voltage will be high. This voltage, without engine running, represents a barometer reading to the ECM

Comparison of this BARO reading with a known good vehicle with the same sensor is a good way to check the accuracy of a suspected bad sensor.

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.