PleasureCraft Engine Group 5.0L, Diagnostic Manual, Page: 224 / 337

5 - 82 Diagnosis 5.0/5.7/6.0/8.1L
MEFI 4 - PCM
7 J2
3
BLK 814
BLK 814
YEL 410
Engine Coolant
Temperature
(ECT) Sensor
Engine
Control
Module
(ECM)
Sensor
Ground
ECT
Sensor
Signal
Engine
Control
Module
(ECM)
B
A
S123
J2
M4060
9-18-02
From MAP
Sensor
From TP
Sensor
•
If DTC 33 is also set, check for open ground CKT 814.
After repairs, clear DTC’s following “Clear DTC’s Procedure.”
Failure to do so may result in DTC’s not properly being
cleared.
Test Description
2. DTC 14 will set if signal voltage indicates a coolant
temperature below -30°C (-22°F).
3. This test simulates a DTC 15. If the ECM recognizes
the low voltage signal and displays a high temperature,
the ECM and wiring are OK.
Circuit Description
The Engine Coolant Temperature (ECT) sensor uses a
thermistor to control the signal voltage to the ECM. The
ECM applies 5 volts on CKT 410 to the sensor. When the
engine coolant is cold, the sensor (thermistor) resistance is
high. As the engine coolant warms up, the sensor resistance
becomes less. See engine coolant temperature sensor table
under “Diagnostic Aids.” At normal operating temperature
(85°C - 95°C or 185°F - 203°F), the voltage will measure
about 1.5-2.0 volts.
Diagnostic Aids
Check for the following conditions:
•
Poor connection at ECM. Inspect harness connectors
for backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals and
poor terminal to wire connection.
•
Damaged harness. Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
ECT display on the scan tool while moving connectors
and wiring harnesses related to the ECT sensor. A
change in the ECT display will indicate the location of
the fault.
•
The scan tool displays engine coolant temperature in
degrees Celsius and Fahrenheit. If the engine is cold
(not running within 8 hours), the scan tool should display
a ECT sensor value within a few degrees of outside
air temperature. This may help aid in diagnosing a
“shifted” coolant sensor. After engine is started, the
temperature should rise steadily and then stabilize at
operating temperature when the thermostat opens.
Engine Coolant Temperature Sensor Table
°C °F OHMS
Temperature vs Resistance Values (Approximate)
100 212 177
80 176 332
60 140 667
45 113 1188
35 95 1802
25 77 2796
15 59 4450
5 41 7280
-5 23 12300
-15 5 21450
-30 -22 52700
-40 -40 100700
DTC 14 - Engine Coolant Temperature (ECT) Sensor Circuit - Low Temp Indicated
(Scan Diagnostics) (High Voltage)