Pinpoint Test DL: Cylinder Head Temperature (CHT) Sensor: Introduction: Notes

NOTE: On a typical vehicle, the CHT sensor is located in the cylinder head and the CHT2 sensor is located in the exhaust manifold.

This pinpoint test is intended to diagnose the following:

cylinder head temperature (CHT) sensor (6G004)
cylinder head temperature 2 (CHT2) sensor (6G004)
harness circuits: CHT, CHT2, and SIGRTN
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. On applications with a CHT2 sensor, the PCM has a single resistor circuit on the CHT2 input. 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 (CHT) Sensor Voltage Graph

Courtesy of FORD MOTOR CO.

CYLINDER HEAD TEMPERATURE (CHT) SENSOR EXPECTED VALUES SPECIFICATIONS

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

CYLINDER HEAD TEMPERATURE 2 (CHT2) SENSOR EXPECTED VALUES SPECIFICATIONS

Temperature		CHT2 Sensor Values
°C	°F	Volts	Resistance (K ohms)
-40	-40	4.995	965.808
-30	-22	4.990	512.947
-20	-4	4.969	283.651
-10	14	4.949	162.585
0	32	4.917	96.248
10	50	4.870	59.173
20	68	4.839	37.387
30	86	4.802	24.216
40	104	4.707	16.043
50	122	4.578	10.851
60	140	4.411	7.487
70	158	4.202	5.269
80	176	3.953	3.775
90	194	3.667	2.750
100	212	3.354	2.038
110	230	3.018	1.523
120	248	2.680	1.155
130	266	2.350	0.8868
140	284	2.040	0.6893
150	302	1.757	0.5418
160	320	1.504	0.4301
170	338	1.282	0.3449
180	356	1.091	0.2791
190	374	0.928	0.2278
200	392	0.789	0.1875
210	410	0.672	0.1554
220	428	0.574	0.1297
230	446	0.491	0.1090
240	464	0.422	0.0921
250	482	0.363	0.0783

Fig 2: Identifying Cylinder Head Temperature (CHT) Sensor Connector

Courtesy of FORD MOTOR CO.

Vehicle	Connector	Pin	Circuit
Transit Connect	A	2 1	SIGRTN CHT
All other vehicles	B	2 1	SIGRTN CHT

Fig 3: Identifying Cylinder Head Temperature 2 (CHT2) Sensor Connector

Courtesy of FORD MOTOR CO.

Pin	Circuit
2	SIGRTN (Signal Return)
1	CHT2 (Cylinder Head Temperature 2)