Mat Sensor Test; Manifold Absolute Pressure (Map) Sensor; Map Sensor Removal And Installation - Mercury 25 EFI Service Manual

MAT Sensor Test

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Use the CDS to test the MAT sensor. If the MAT sensor reads 5 °C ( 41 °F) ± difference from the ambient air temperature,
replace the MAT sensor. Perform the MAT sensor test when the engine is cold.
MAT Sensor Specifications
20 °C (68 °F)
80 °C (176 °F)
1. Measure the resistance of the MAT sensor.
2. Connect the DMT 2004 Digital Multimeter to the contact pins on the MAT sensor.
3. Compare the resistance shown on the DMT 2004 Digital Multimeter with the MAT sensor specifications. Replace the MAT
sensor if the resistance is out of the specifications.
DMT 2004 Digital Multimeter

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor measures the changes in the intake manifold pressure. It is located at the top of the intake manifold. The
signal voltage from the MAP sensor received by the ECM is referenced as the atmosphere barometric pressure. This
information is used by the ECM as an indication of altitude during start up. The MAP will change the signal voltage as a result
of engine load and speed changes. The MAP sensor signal voltage is used by the ECM programed logic to determine the
optimum fuel injection timing, ignition timing, and fuel injection duration.

MAP Sensor Removal and Installation

MAP Sensor Removal
1. Disconnect the engine harness connector from the MAP sensor.
90-8M0105568 eng MARCH 2016
b
a
© 2016 Mercury Marine
a - ECM engine harness connector
b - Manifold air temperature (MAT) sensor
22592
2.35–2.55 ohms
0.3–0.035 ohms
23015
91‑892647A01
Ignition
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