Manifold Absolute Pressure (MAP) Sensor
The manifold absolute pressure (MAP) sensor measures the absolute atmospheric pressure in the intake manifold pressure.
When the ignition key switch is first turned ON, the MAP sensor reads the ambient atmospheric pressure, which the PCM
records as BARO (viewable in CDS G3 Live Data). When the engine is running, the PCM uses the MAP sensor to monitor
changes in manifold pressure as the throttle opens and adjusts fuel delivery accordingly. The MAP sensor also allows the
system to compensate for variations in altitude and weather.
The MAP sensor is located next to the throttle body, and it is connected to the intake manifold via a reference hose.
a - MAP sensor
b - Reference hose
MAP Sensor Test
Monitor the manifold absolute pressure (data item MAP_Angle) in the CDS G3 Live Data screen. The value should vary
between idle and wide‑open throttle RPMs, as shown following.
Example MAP Sensor Readings
At idle 35–48 kPa (5–7 psi)
At wide‑open throttle
Within 15% of BARO
CDS G3 Interface Kit 8M0138392
If the MAP_Angle does not appear to vary with engine RPM, shake or move the sensor harness and connector. If the pressure
begins to change, look for a broken, loose, or corroded wire.
Continue testing with the engine OFF:
1. Disconnect the engine harness connector from the sensor.
2. Visually inspect the sensor pins and the wires to the connector. Look for broken, bent, or corroded pins at the sensor and
loose, broken, or corroded wires at the connector.
3. Check the MAP sensor with a digital ohmmeter between pins A, B, and C.
MAP sensor with attached hose
a - Pin A
b - Pin B
c - Pin C
DMT 2004 Digital Multimeter 91‑892647A01
Meter Test Leads
Meter Scale
Reading
Red Black At 21 °C (70 °F)
Pin A Pin B Auto 4.28 kΩ ± 30%
Pin A Pin C Auto 1.93 kΩ ± 30%
Pin B Pin C Auto 6.48 kΩ ± 30%
Sensors
Page 5A-26 © 2018 Mercury Marine 90-8M0146617 eng JULY 2018
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