Coolant Temperature Sensor Jeep 4.0 and 2.5

Coolant Temperature Sensor Testing

How do you test it to see if it is bad?

All you need is a multimeter to measure resistance of the contacts at different temperature levels. Also a way to vary the temperature of the sensor. Something like a pan of water on the stove top over low heat. Use a thermometer to measure the water temp as it climbs. Not the water temp as you measure the resistance and compare it to the chart below.

Below is the Temp to resistance chart for the Jeep YJ & XJ. It may work for other fuel injected Jeeps as well.

Temperature

Resistance (Ohms)

C

F

Min

Max

-40

-40

291,490

381,710

-20

-4

85,850

108,390

-10

14

49,250

61,430

0

32

29,330

35,990

10

50

17,990

21,810

20

68

11,370

13,610

25

77

9,120

10,880

30

86

7,370

8,750

40

104

4,900

5,750

50

122

3,330

3,880

60

140

2,310

2,670

70

158

1,630

1,870

80

176

1,170

1,340

90

194

860

970

100

212

640

720

110

230

480

540

120

248

370

410

Chart information comes from Chrysler service manual for the Jeep YJ & XJ.