4.10
9850043 R01 - 2017-2021 RANGER 500 / 570 Service Manual
© Copyright Polaris Inc.
ENGINE COOLANT TEMPERATURE SENSOR (ETC)
ECT OVERVIEW
Mounted on the cylinder head, the engine temperature
sensor measures coolant temperature. The engine
temperature sensor is a Negative Temperature
Coefficient (NTC) type sensor, as the temperature
increases, the resistance decreases. This signal is
processed by the ECU for determining the fuel and
ignition requirements during operation. The ECU also
uses this signal to determine when to activate the fan.
ECT SENSOR TEST
SYSTEM OPERATION TEST
To quickly rule out other components and wiring related
to the ECT, disconnect the main wiring harness from the
ECT sensor and start the engine. After a few seconds,
the fan should turn on and the “Check Engine” indicator
should display on the instrument cluster. This indicates
all other components are working properly.
RESISTANCE VERSUS TEMPERATURE
TEST
CAUTION
Contact with boiling water or steam may cause burns.
1. Disconnect the main wiring harness from the ECT
sensor on the engine.
2. Remove the ECT sensor.
3. Fill a pot of water half way.
4. Place the pot of water on a hot plate.
5. Place the sensor / tip of a thermometer in the water,
ensure the display is legible as you will reference the
thermometer throughout the test.
6. Safely position the ECT so that the sensor is
submerged in water from the threads down and the
connector may be readily probed.
NOTICE
Use a wire or other type of prop to ensure the sensor is
properly supported and the tip of the sensor is touching
water only.
7. Prepare a table similar to the one below, then heat
the water and document the resistance measured
between pin 1 and pin 2 as the water and sensor
warm. If the sensor tests out of tolerance, the sensor
should be replaced.
ECT SENSOR RESISTANCE READINGS
TEMPERATURE °F (°C)
RESISTANCE
68 °F (20 °C)
2.5 k Ω ± 6%
86 °F (30 °C)
1.7 k Ω ± 6%
104 °F (40 °C)
1.2 k Ω ± 6%
122 °F (50 °C)
834 Ω ± 6%
140 °F (60 °C)
596 Ω ± 6%
158 °F (70 °C)
435 Ω ± 6%
176 °F (80 °C)
323 Ω ± 6%
194 °F (90 °C)
243 Ω ± 6%
212 °F (100 °C)
186 Ω ± 6%
ENGINE ELECTRICAL
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