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7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
ECT Circuit Operation
Figure 429 ECT circuit diagram
The ECT sensor is supplied with a 5 V reference
voltage at Pin 2 from ECM Pin X1–8. The sensor is
grounded at Pin 1 through the signal ground at the
ECM Pin X1–6. As the coolant temperature increases
or decreases, the sensor changes resistance and
provides the coolant temperature signal voltage at the
ECM. The signal voltage is monitored by the ECM to
determine the temperature of the coolant.
Fault Detection / Management
The ECM continuously monitors the signal of the
ECT sensor to determine if the signal is within an
expected range. If the ECM detects an out of range
high or low, the ECM will ignore the ECT signal and
assume an engine coolant temperature of -20 °C
(-4 °F) for starting and 82 °C (180 °F) for engine
running conditions. When this occurs, the EWPS,
CAP, IST, cold idle advance, and coolant temperature
compensation features are disabled.
ECT Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamp.
DTC 114
ECT signal out-of-range low
•
DTC 114 set by the ECM when the ECT signal is
less than 0.127 V for more than 0.35 second.
•
DTC 114 can set due to a short to ground in the
signal circuit or a failed ECT sensor.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
•
When DTC 114 is active the amber ENGINE lamp
is illuminated.
DTC 115
ECT signal out-of-range high
•
DTC 115 set by the ECM when the ECT signal is
more than 4.6 V for more than 0.35 second.
•
DTC 115 can set due to an open signal or ground
circuit, a short to a voltage source, or a failed ECT
sensor.
•
When DTC 115 is active the amber ENGINE lamp
is illuminated.
Tools
•
EST with MasterDiagnostics® software
•
EZ-Tech® interface cable
•
Digital Multimeter (DMM)
•
3-Banana Plug Harness
•
500 Ohm Resistor Harness
•
Breakout Box
•
Breakout Harness
•
Terminal Test Adapter Kit
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
393
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