Wiring sensor ground (Pin 2) to chassis ground instead of the dedicated ECU ground pin. Result: The alternator noise and ignition interference modulate the sensor readings. Your MAP sensor will bounce 10 kPa with every spark. Solution: Sensor ground must be isolated and run exclusively to the designated pin on the ECU.

: This paper details a system-level approach, breaking down the ECU into functional sections (Charging, Ignition, Fuel) and discussing the integration of analog and digital interfacing circuits on a single PCB.