4. Install the cold air intake assembly. Refer to the appropriate service manual.
• Ensure that the reference hose is secured to the assembly with a cable tie.
• Ensure that the hose clamp is securely tightened.
• Ensure that the oil level dipstick is properly inserted into the dipstick tube.
Engine Coolant Temperature (ECT) Sensor
The engine coolant temperature (ECT) sensor is a thermistor immersed in the engine coolant path. It supplies the PCM with
engine temperature information. The PCM adjusts the timing and the amount of fuel delivered according to the water
temperature in the exhaust manifold. Low coolant temperature produces high resistance, while high temperature causes low
resistance. Outside air temperature and the temperature of the water that the engine is operating in will directly affect the
engine block temperature.
The engine coolant temperature (ECT) sensor is located at the top of the exhaust manifold.
a - Top of the exhaust manifold
b - Engine coolant temperature sensor
ECT Sensor Test
Monitor the engine coolant temperature (data item ECT) on the CDS G3 Live Data screen. With the engine not running, block
temperature should be approximately the same as the ambient air temperature. After the engine is started, the temperature
sensor should indicate a rise in block temperature to approximately 60–70 °C (140–158 °F).
CDS G3 Interface Kit
8M0138392
If there is not an obvious change in block temperature sensor values, shake or move the sensor harness and connector. If the
temperature begins to change, look for a broken, loose, or corroded wire.
Continue testing with the engine OFF:
1. Disconnect the engine harness from the sensor harness.
2. Perform a visual inspection of the sensor pins and the wires coming from the connector. Look for broken, bent, or corroded
pins at the sensor and loose, broken, or corroded wires at the connector.
3. Test the sensor with an ohmmeter.
a. Remove the sensor from the cylinder block.
b. Immerse the tip of the sensor in a controlled temperature medium. If the readings do not match those in the table,
replace the sensor and retest.
a -
Pin A—ground (–)
b - Cylinder block temperature sensor
c - Pin B—engine coolant temperature signal (+)
DMT 2004 Digital Multimeter 91‑892647A01
Sensors
90-8M0146617 eng JULY 2018 © 2018 Mercury Marine Page 5A-17
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