PINPOINT TEST DX: Engine Coolant Temperature (ECT) 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.

NOTE: Engine coolant temperature must be greater than 10°C (50°F) to pass the KOEO self-test and greater than 82°C (180°F) to pass the KOER self-test. to accomplish this, the engine must be at normal operating temperature.

This pinpoint test is intended to diagnose the following:

engine coolant temperature (ECT) sensor (12A648)
harness circuits: ECT and SIGRTN
powertrain control module (PCM) (12A650)

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

Fig 1: Engine Coolant Temperature Sensor Voltage Graph

TEMPERATURE SENSOR VOLTAGE AND RESISTANCE SPECIFICATIONS

Temperature		Temperature Sensor Values
°C	°F	Voltage	Resistance (K ohms)
120	248	0.28	1.18
110	230	0.36	1.55
100	212	0.47	2.07
90	194	0.61	2.80
80	176	0.80	3.84
70	158	1.05	5.37
60	140	1.37	7.70
50	122	1.77	10.97
40	104	2.23	16.15
30	86	2.74	24.27
20	68	3.26	37.30
10	50	3.73	58.75
0	32	4.14	95.85
-10	14	4.45	160.31

Fig 2: Engine Coolant Temperature (ECT) Sensor Connector

Vehicle	Connector	Pin	Circuit
Five Hundred, Freestyle, Montego	A	1 2	SIGRTN ECT
All other vehicles	A	2 1	SIGRTN ECT

Powertrain Control Module (PCM) Connector

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

Vehicle	Connector	Pin	Circuit
Explorer, Explorer Sport Trac, Mountaineer, Mustang, Ranger	170 Pin	E57 E58 E18	VREF SIGRTN ECT
Fusion, Milan	140 Pin	E57 E58 E18	VREF SIGRTN ECT
Taurus	104 Pin	90 91 38	VREF SIGRTN ECT
All other vehicles	150 (50-50-50) Pin	E40 E41 E21	VREF SIGRTN ECT