The purpose of this test is to evaluate the voltage output and response time of an analogue MAP sensor during engine idle, WOT and over-run conditions.
Plug a BNC test lead into Channel A on the PicoScope, place a black clip on the test lead with the black moulding (negative) and a Back-pinning Probe onto the test lead with the red moulding (positive). Place the black clip onto the battery negative terminal and probe the air intake pressure sensor's output terminal with the Back-pinning Probe as illustrated in Figure 1. If you cannot reach the terminal or plug with a probe, then you may be able to use a breakout lead or box if you have one available.
When testing the air intake pressure sensor, it may take several attempts to 'centralise' the waveform when capturing the output.
With the example waveform displayed on the screen you can now hit the space bar to start looking at live readings. Snap the accelerator quickly from idle to full throttle and observe the waveform.
The output waveform produced by the air intake pressure sensor will be similar the example shown. The voltage seen on the oscilloscope will be proportionate to the boost pressure produced by the engines turbocharger.
The voltage at idle will be around 1.5 - 2.0 volts and will be seen to rise as the pressure increases, reaching a maximum voltage of approximately 4.0 volts. The 'hash' that is evident on the waveform is a result of a slight pressure change due to the engine's induction strokes.
The sensor is connected into the inlet air supply and is of the conventional piezoelectric strain gauge variety.
The sensor has three electrical connections, as follows:
The pressure sensor supplies the ECM with a voltage that is proportional to the pressure in the inlet manifold.
This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.
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