Pinpoint Test DN: Motor Electronics Coolant Temperature (MECT) Sensor: Introduction

WARNING: THIS VEHICLE IS EQUIPPED WITH HIGH VOLTAGE CABLES, COMPONENTS, AND WIRING. THE HIGH VOLTAGE WARNING LABELS CONTAINING THE HIGH VOLTAGE SYMBOL ARE LOCATED ON EACH HIGH VOLTAGE COMPONENT. HIGH VOLTAGE CABLES AND WIRING ARE ORANGE IN COLOR. CERTIFIED RUBBER INSULATING GLOVES AND A FACE SHIELD MUST BE WORN WHEN WORKING WITH THE HIGH VOLTAGE CABLES, COMPONENTS, OR WIRING. THE IGNITION KEY MUST BE CYCLED TO THE OFF POSITION FOR A MINIMUM OF 5 MINUTES, AND THE HIGH VOLTAGE TRACTION BATTERY SERVICE DISCONNECT PLUG PLACED IN THE SERVICING/SHIPPING POSITION BEFORE DISCONNECTING THE HIGH VOLTAGE CABLES. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY OR DEATH.
DO NOT DISCONNECT, DISABLE, OR TOUCH THE HIGH VOLTAGE CABLES, COMPONENTS, OR WIRING DURING THE MODULE REPROGRAMMING PROCEDURE BECAUSE HIGH VOLTAGE IS PRESENT. THE HIGH VOLTAGE WARNING LABELS CONTAINING THE HIGH VOLTAGE SYMBOL ARE LOCATED ON EACH HIGH VOLTAGE COMPONENT. HIGH VOLTAGE CABLES AND WIRING ARE ORANGE IN COLOR. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY OR DEATH.

NOTE: Carefully check the motor electronics cooling system integrity. Over-temperature diagnostic trouble codes (DTCs) can be stored as a result of extreme driving conditions. Under normal operating conditions, the motor electronics coolant temperature should not exceed 65°C (150°F) and maintain a temperature of approximately 11°C (20°F) over ambient temperature during a steady cruise above 65 km/h (40 mph).

This pinpoint test is intended to diagnose the following:

MECT (12B579)
harness circuits: MECT, VREF, 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: Temperature Sensor Voltage And Resistance Characteristic Graph

Courtesy of FORD MOTOR CO.

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: Motor Electronics Coolant Temperature (MECT) Sensor Connector

Courtesy of FORD MOTOR CO.

MOTOR ELECTRONICS COOLANT TEMPERATURE (MECT) SENSOR CONNECTOR PIN REFERENCE CHART

Pin	Circuit
2	SIGRTN (Signal Return)
1	MECT (Motor Electronics Coolant Temperature)

Fig 3: Powertrain Control Module (PCM) Connector

Courtesy of FORD MOTOR CO.

POWERTRAIN CONTROL MODULE (PCM) CONNECTOR PIN REFERENCE CHART

Pin	Circuit
B66	VREF (Reference Voltage)
T40	SIGRTN (Signal Return)
T29	MECT (Motor Electronics Coolant Temperature)