Component Diagnostic Charts - Throttle Body Fuel Injection

Chart C-1D:

Wiring Diagram For MAP Sensor:

CIRCUIT DESCRIPTION:

The Manifold Absolute Pressure (MAP) sensor measures manifold pressure (vacuum) and sends that signal to the ECM. The MAP sensor is mainly used for engine load, which is an input for spark advance and fuel calculations. The MAP sensor is also used to determine the barometric pressure.


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. This checks MAP sensor output voltage to the ECM. This voltage, without the engine running, represents a barometer reading to the ECM. Comparison of this BARO sensor reading with a known good sensor is a good way to check the accuracy of a "suspect" sensor. The readings should be within 0.4 volts of each other.
2. Applying 34 kPa (10" Hg.) of vacuum to the MAP sensor should cause the voltage to be 1.2 - 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 a leak or a restriction. Be sure that no other vacuum devices are connected to the MAP sensor hose.