Checking the coolant temperature sensor (Hyundai Sonata EF)

Contents: General information ⇓ Troubleshooting Guide ⇓ Checking the sensor ⇓ Checking with a tester ⇓ Checking with a voltmeter ⇓

General information

The coolant temperature sensor is installed in the cooling jacket channel of the cylinder head. It detects the temperature of the engine coolant and transmits a signal to the electronic engine control unit. The sensor is a thermistor sensitive to temperature changes. The resistance of the sensor decreases as the temperature of the engine coolant increases.

The engine control unit evaluates the coolant temperature based on the sensor signal voltage and adjusts the injector opening signal duration and ignition advance angle. If the coolant temperature is very low, the engine control unit enriches the air-fuel mixture (increases the injector opening signal duration) and increases the ignition advance angle (sets early ignition).

Engines 2.0L/2.4L

Engine 2.7 l

Troubleshooting Guide

If the increased idle speed during warming up of a cold engine is not normal, or warming up of the engine is accompanied by black smoke from the exhaust pipe, then, most likely, the cause of this may be the coolant temperature sensor.

Checking the sensor

1. Remove the coolant temperature sensor from the engine intake manifold.

2. Immerse the measuring part of the sensor in water with a known temperature and measure the resistance between the sensor terminals.

Table. Nominal values.

Temperature	Resistance (kOhm)
0°C	5,9
20°C	2,5
40°C	1,1
80°C	0,3

3. If the measured resistance differs from the nominal values, replace the coolant temperature sensor.

Checking with a tester

1. Conditions for conducting the inspection.

Ignition switch: in the "ON" position or the engine is running.

2. Performing the check:

Read the tester readings (coolant temperature recorded by the sensor).