Test DL: Cylinder Head Temperature Sensor: Description

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Mountaineer, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

On vehicles that do not use an ECT sensor, a CHT sensor is used to determine engine coolant temperature in place of ECT sensor. In this case, PCM may store both CHT and ECT DTCs. To cover entire temperature range of both CHT and ECT sensors, PCM has a dual switching resistor circuit on CHT input. For a graph showing temperature switching from COLD END line to HOT END line with increasing temperature and back with decreasing temperature, see illustration. See Fig 1.

NOTE: Within the temperature to voltage overlap zone, it is possible to have either a COLD END or HOT END voltage at the same temperature. For example; at 194°F (90°C), voltage could read either 0.60 volt or 3.71 volts. Refer to CHT SENSOR SPECIFICATIONS table for temperature to voltage expected values.

Fig 1: CHT Sensor Cold End & Hot End Line Graph

Courtesy of FORD MOTOR CO.

CHT SENSOR SPECIFICATIONS ⁽¹⁾

Temperature °F (°C)

Volts

Ohms

-40 (-40)

4.89

965,808

-22 (-30)

4.81

513,019

-4 (-20)

4.67

283,664

14 (-10)

4.45

162,584

32 (0)

4.14

96,255

50 (10)

3.73

59,175

68 (20)

3.26

37,387

86 (30)

2.74

24,215

104 (40)

2.23

16,043

122 (50)

1.76

10,850

140 (60)

1.36

7487

158 (70)

1.04

5268

176 (80) ⁽²⁾

.79 Or 3.99

3775

185 (85) ⁽²⁾

.69 Or 3.86

3215

194 (90) ⁽²⁾

.60 Or 3.71

2750

203 (95) ⁽²⁾

.53 Or 3.56

2361

212 (100) ⁽²⁾

.46 Or 3.41

2034

230 (110)

3.07

1523

248 (120)

2.74

1155

266 (130)

2.41

.887

284 (140)

2.10

689

302 (150)

1.81

542

320 (160)

1.55

430

338 (170)

1.33

345

356 (180)

1.13

279

374 (190)

.96

228

392 (200)

.82

188

410 (210)

.70

155

428 (220)

.60

130

446 (230)

.51

109

464 (240)

.44

482 (250)

.35

500 (260)

.33

⁽¹⁾	Value may vary by 15 percent.

⁽²⁾	At this temperature, there is a voltage overlap zone due to a dual switching resistor circuit on CHT input. It is possible to have either a cold end (low voltage) or hot end (high voltage) measurement at the same temperature. Either voltage specification listed is correct.

Fig 2: Identifying CHT Sensor Harness Connector Terminals (Escape & Focus 2.0L 4V)

Courtesy of FORD MOTOR CO.

Fig 3: Identifying CHT Sensor Harness Connector Terminals (All Others)

Courtesy of FORD MOTOR CO.