Air intake pressure sensor - Bosch common rail diesel

The purpose of this test is to evaluate the voltage output and response time of an analog MAP sensor during engine idle, WOT and over-run conditions.  

How to perform the test

  1. Identify the Pressure Sensor output signal terminal, at the control unit if access allows. Connect to Channel A of your PicoScope.

  2. Start the engine.

  3. Minimise the help screen and with the example waveform displayed on the screen PicoScope has already selected suitable scales for you to capture a waveform. Select GO or press the space bar to see live data.

  4. Carry out a WOT test to capture your waveform.

Example waveform

Waveform notes

The voltage at idle is 1.5 - 2.0 volts and rises as the pressure increases, reaching a maximum of approximately 4.0 volts. On overrun the voltage gradually drops back to idle levels. The hash that is evident on the waveform is a result of a slight pressure change due to engine induction strokes.

Waveform Library

The Waveform Library has 50 examples of analog air intake pressure sensors listed.

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and filter for manifold absolute pressure sensor (analog).

Technical information

The sensor is mounted into the inlet air supply and is usually a piezoelectric strain gauge.

The sensor has three electrical connections.

  • Pin 1 = Battery volts supply.
  • Pin 2 = earth circuit.
  • Pin 3 = output signal volts.

The pressure sensor supplies the Engine Control Module (ECM) with a voltage that is proportional to the pressure within the intake system.

Note. A WOT test on a turbo charged engine will display lower results than you would get on an engine under load. However the WOT waveform will show the pressure changes within the system.


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.

Suitable accessories

  • Back-pinning Probe Set


  • Flexible Back-pinning Probe


  • PicoScope Battery Clip


  • Large Dolphin/Gator Clips


  • Premium Test Lead: BNC to 4 mm, 3 m


  • Premium Test Leads: Set of four leads 3 m (TA125 - TA128)


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Guided test: Analog (Turbo Diesel)