The purpose of this test is to investigate the operation of a digital Manifold Air Pressure (MAP) sensor during idle, free revving, and overrun engine operating conditions.
This known good waveform has the following characteristics:
MAP sensors respond to the air pressure within the intake manifold and allow the Engine Control Module (ECM) to estimate two important parameters:
The sensor can be mounted on the manifold housing or remotely, with pipework connecting the sensing element to the manifold volume.
The internal circuitry requires three electrical circuit connections to operate:
The output frequency of a digital MAP sensor increases with increasing absolute pressure (or decreasing vacuum if referenced relative to atmospheric pressure). Therefore, on a normally aspirated gasoline engine, the sensor output is normally highest (around 160 Hz) at atmospheric pressure and lowest (around 80 – 100 Hz) when there is a significant depression within the intake manifold, such as at idle or on overrun.
Symptoms of a faulty MAP sensor:
Possible failures that can cause erroneous MAP sensor signals are:
Selection of component related Diagnostic Trouble Codes (DTCs):
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