PINPOINT TEST DL: Cylinder Head Temperature (CHT) Sensor: Introduction

WARNING: This page does not describe the selected car, but rather 35 other vehicles, including the 2007 Mercury Mountaineer, 2007 Mercury Monterey, 2007 Mercury Montego, 2007 Mercury Milan, and 2007 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.

This pinpoint test is intended to diagnose the following:

cylinder head temperature (CHT) sensor (6G004)
harness circuits: CHT, VREF, and SIGRTN
powertrain control module (PCM) (12A650)

On applications that do not use an engine coolant temperature (ECT) sensor, the CHT sensor is used to determine the engine coolant temperature. To cover the entire temperature range of both the CHT and ECT sensors, the PCM has a dual switching resistor circuit on the CHT input. A graph showing the temperature switching from the COLD END line to the HOT END line, with increasing temperature and back with decreasing temperature is included. Note the temperature to voltage overlap zone. Within this zone it is possible to have either a COLD END or HOT END voltage at the same temperature. For example, at 90°C (194°F) the voltage could read either 0.60 volt or 3.71 volts. Refer to the table for the temperature to voltage expected values.

Voltage values calculated for VREF = 5 volts. These values can vary by 15% due to sensor and VREF variations.

Fig 1: Cylinder Head Temperature Sensor Voltage Graph

CYLINDER HEAD TEMPERATURE SENSOR EXPECTED VALUES

Temperature		CHT Sensor Values
°C	°F	Cold End (volts)	Hot End (volts)	Resistance (K ohms)
-40	-40	4.89	-	965.808
-30	-22	4.81	-	513.019
-20	-4	4.67	-	283.664
-10	14	4.45	-	162.584
0	32	4.14	-	96.255
10	50	3.73	-	59.175
20	68	3.26	-	37.387
30	86	2.74	-	24.215
40	104	2.23	-	16.043
50	122	1.76	-	10.85
60	140	1.36	-	7.487
70	158	1.04	-	5.268
80	176	0.79	3.99	3.775
85	185	0.69	3.86	3.215
90	194	0.60	3.71	2.75
95	203	0.53	3.56	2.361
100	212	0.46	3.41	2.034
110	230	-	3.07	1.523
120	248	-	2.74	1.155
130	266	-	2.41	0.8866
140	284	-	2.10	0.6891
150	302	-	1.81	0.5417
160	320	-	1.55	0.4301
170	338	-	1.33	0.3449
180	356	-	1.13	0.2791
190	374	-	0.96	0.2278
200	392	-	0.82	0.1875
210	410	-	0.70	0.155
220	428	-	0.60	0.130
230	446	-	0.51	0.109
240	464	-	0.44	0.092
250	482		0.35	0.078
260	500		0.33	0.067

Fig 2: Cylinder Head Temperature (CHT) Sensor Connector

Pin	Circuit
2	SIGRTN (Signal Return)
1	CHT (Cylinder Head Temperature)

Powertrain Control Module (PCM) Connector

For PCM connector views or reference values, refer to the REFERENCE VALUES article.

Vehicle	Connector	Pin	Circuit
Edge, F-150, Mark LT, MKX	190 Pin	E57 E58 E41	VREF SIGRTN CHT
Escape, Focus, Mariner	150 (50-50-50) Pin	E40 E41 E33	VREF SIGRTN CHT
Expedition, Fusion, Milan, MKZ, Navigator	140 Pin	E57 E58 E41	VREF SIGRTN CHT
Freestar/Monterey	104 Pin	90 91 38	VREF SIGRTN CHT
All other vehicles	170 Pin	E57 E58 E41	VREF SIGRTN CHT